title: Plotly Blank Sankey Diagram with no errors
body: <p>I'm attempting to plot a Sankey diagram using plotly and I get a blank output with no python or inspection errors.</p>
  
  <p>The plot class I created is the following:</p>
  
  <pre><code>from typing import *
  import logging
  import pandas as pd
  import plotly
  import seaborn as sns
  
  from .visualizer import AbstractVisualizer
  
  
  class PlotlyVisualizer(AbstractVisualizer):
      logger = logging.getLogger('PlotlyVisualizer')
  
      def __init__(self, config: dict) -&gt; None:
          """
          Plotly Visualizer
          """
          super().__init__(config=config)
  
      @staticmethod
      def __generate_sankey_figure__(nodes_df: pd.DataFrame, edges_df: pd.DataFrame, color_list: List,
                                     title: str = 'Sankey Diagram'):
          # creating the sankey diagram
          data = dict(
              type='sankey',
              node=dict(
                  hoverinfo="all",
                  pad=15,
                  thickness=20,
                  line=dict(
                      color="black",
                      width=0.5
                  ),
                  label=nodes_df['Node'],
                  color=color_list
              ),
              link=dict(
                  source=edges_df['Source'],
                  target=edges_df['Target'],
                  value=edges_df['Count']
              )
          )
  
          layout = dict(
              title=title,
              font=dict(
                  size=10
              )
          )
  
          fig = dict(data=[data], layout=layout)
          return fig
  
      def plot(self, nodes_df: pd.DataFrame, edges_df: pd.DataFrame, attribute_cols: List, name_col: str):
          # Generate color palette
          color_palette = list(sns.color_palette(None, nodes_df.count()[0]).as_hex())
          color_list = color_palette
          fig = self.__generate_sankey_figure__(nodes_df=nodes_df, edges_df=edges_df, color_list=color_list,
                                                title=self.__config__['plot_name'])
          self.logger.info(fig)
          filename = "{}/{}.html".format(self.__config__['target_path'], self.__config__['plot_name'])
  
          plotly.offline.plot(fig, validate=True, filename=filename)
  </code></pre>
  
  <p>The nodes_df and edges_df that I'm using as input is like this:</p>
  
  <p><code>nodes_df:</code></p>
  
  <pre><code>                               Node  Count
  0                New democracy_2019    158
  1                New democracy_2007    153
  2                       Syriza_2015    149
  3                        Pasok_2007    102
  4                       Syriza_2019     86
  5                New democracy_2015     77
  6          Movement for change_2019     22
  7                          Kke_2007     22
  8                  Golden dawn_2015     17
  9                    The river_2015     17
  10   Communist party of greece_2015     15
  11   Communist party of greece_2019     15
  12                      Syriza_2007     14
  13          Independent greeks_2015     13
  14  Pasok-democratic alignment_2015     13
  15                        Laos_2007     10
  16              Greek solution_2019     10
  17                      Mera25_2019      9
  </code></pre>
  
  <p><code>edges_df:</code></p>
  
  <pre><code>                             Source                           Target  Count
  0                New democracy_2015               New democracy_2019     28
  1                New democracy_2007               New democracy_2015     22
  2                       Syriza_2015                      Syriza_2019     18
  3                New democracy_2007               New democracy_2019     16
  4                        Pasok_2007  Pasok-democratic alignment_2015      6
  5                        Pasok_2007         Movement for change_2019      4
  6                          Kke_2007   Communist party of greece_2019      3
  7    Communist party of greece_2015   Communist party of greece_2019      2
  8                         Laos_2007               New democracy_2019      2
  9                        Pasok_2007                      Syriza_2019      2
  10  Pasok-democratic alignment_2015         Movement for change_2019      2
  11                      Syriza_2015                      Mera25_2019      1
  12                      Syriza_2007                      Syriza_2019      1
  13                      Syriza_2007                      Syriza_2015      1
  14                       Pasok_2007                      Syriza_2015      1
  15               New democracy_2019               New democracy_2019      1
  16                       Pasok_2007                      Mera25_2019      1
  17               New democracy_2015               New democracy_2015      1
  18               New democracy_2007               New democracy_2007      1
  19               New democracy_2007          Independent greeks_2015      1
  20                        Laos_2007               New democracy_2015      1
  21                        Laos_2007              Greek solution_2019      1
  22                   The river_2015               New democracy_2019      1
  </code></pre>
  
  <p>And finally the figure dictionary has the following structure:</p>
  
  <pre><code>{'data': 
    [
      {'type': 'sankey', 
        'node': 
        {'hoverinfo': 'all', 
          'pad': 15, 
          'thickness': 20, 
          'line': 
          {'color': 'black', 'width': 0.5}, 
          'label': 0                  New democracy_2019
                   1                  New democracy_2007
                   2                         Syriza_2015
                   3                          Pasok_2007
                   4                         Syriza_2019
                   5                  New democracy_2015
                   6            Movement for change_2019
                   7                            Kke_2007
                   8                    Golden dawn_2015
                   9                      The river_2015
                   10     Communist party of greece_2015
                   11     Communist party of greece_2019
                   12                        Syriza_2007
                   13            Independent greeks_2015
                   14    Pasok-democratic alignment_2015
                   15                          Laos_2007
                   16                Greek solution_2019
                   17                        Mera25_2019
                  Name: Node, dtype: object, 
          'color': ['#1f77b4', '#ff7f0e', '#2ca02c', '#d62728', '#9467bd', '#8c564b', '#e377c2', '#7f7f7f', '#bcbd22', '#17becf', '#1f77b4', '#ff7f0e', '#2ca02c', '#d62728', '#9467bd', '#8c564b', '#e377c2', '#7f7f7f']}, 
          'link': 
          {'source':  0                  New democracy_2015
                      1                  New democracy_2007
                      2                         Syriza_2015
                      3                  New democracy_2007
                      4                          Pasok_2007
                      5                          Pasok_2007
                      6                            Kke_2007
                      7      Communist party of greece_2015
                      8                           Laos_2007
                      9                          Pasok_2007
                      10    Pasok-democratic alignment_2015
                      11                        Syriza_2015
                      12                        Syriza_2007
                      13                        Syriza_2007
                      14                         Pasok_2007
                      15                 New democracy_2019
                      16                         Pasok_2007
                      17                 New democracy_2015
                      18                 New democracy_2007
                      19                 New democracy_2007
                      20                          Laos_2007
                      21                          Laos_2007
                      22                     The river_2015
                      Name: Source, dtype: object, 
            'target': 0                  New democracy_2019
                      1                  New democracy_2015
                      2                         Syriza_2019
                      3                  New democracy_2019
                      4     Pasok-democratic alignment_2015
                      5            Movement for change_2019
                      6      Communist party of greece_2019
                      7      Communist party of greece_2019
                      8                  New democracy_2019
                      9                         Syriza_2019
                      10           Movement for change_2019
                      11                        Mera25_2019
                      12                        Syriza_2019
                      13                        Syriza_2015
                      14                        Syriza_2015
                      15                 New democracy_2019
                      16                        Mera25_2019
                      17                 New democracy_2015
                      18                 New democracy_2007
                      19            Independent greeks_2015
                      20                 New democracy_2015
                      21                Greek solution_2019
                      22                 New democracy_2019
                      Name: Target, dtype: object,
            'value':  0     28
                      1     22
                      2     18
                      3     16
                      4      6
                      5      4
                      6      3
                      7      2
                      8      2
                      9      2
                      10     2
                      11     1
                      12     1
                      13     1
                      14     1
                      15     1
                      16     1
                      17     1
                      18     1
                      19     1
                      20     1
                      21     1
                      22     1
                      Name: Count, dtype: int64}}], 
    'layout': 
      {'title': 'Sankey_2007_2015_2019', 
        'font': {'size': 10}}
      }
  </code></pre>
  
  <p>As stated at the beginning, I get not python errors and no inspection errors on the browser, just a rendered blank html file.</p>
  
  <p>Thanks in advance.</p>