title: Filter Dask DataFrame rows by specific values of index
body: <p>Is there effective solution to select specific rows in Dask DataFrame?
  I would like to get only those rows which index is in a closed set (using the <code>isin</code> function is not enough efficient for me).</p>
  <p>Are there any other effective solutions than             <code>ddf.loc[ddf.index.isin(list_of_index_values)]</code>
  <code>ddf.loc[~ddf.index.isin(list_of_index_values)]</code>
  ?</p>