title: Iterate through a dask series (getting unique values from dask series to list)
body: <p>I need to iterate through unique values from a dask dataframe. I used .unique() to get the unique values of the columns but now i'm given a dask object that I cannot use to iterate. I need to know how to get these unique values out of this dask object into a list (or something similar) so I can use those values to iterate through the dask dataframe.</p>
  
  <pre><code>df = dd.read_csv('file.csv')
  df.column1.unique()
  for unique_value in column1_array:
      print(unique_value)
  </code></pre>
  
  <p>This is the error I get:
  NotImplementedError: Series getitem in only supported for other series objects with matching partition structure</p>