title: Using Dataframe calls with integer like column names
body: <p>I'm trying to extract some information from my data set. Column names are City, TOTAL, 2018, 2019, 2020, 2021</p>
  <p>I can use dfc.City and dfc.TOTAL and they work perfectly fine.
  How can I call 2018 and rest like this?</p>
  <p>dfc['2018'] doesn't seem to work for me :/</p>
  <p>This code is in @app.callback for plotly dash. Weird enough dfc.City,dfc.TOTAL, dfc['2018'] works outside the callback.</p>
  <p>Is there any fix or workaround for this?</p>
  <p>Thank you</p>
  <pre><code>fig = go.Figure(data=[go.Table(
      header=dict(values=list(dfc.columns[1:]),
                  fill_color='paleturquoise',
                  align='left'),
      cells=dict(values=[dfc.City,dfc.TOTAL ],
                 fill_color='lavender',
                 align='left'))
  </code></pre>