title: groupby shapely type in geopandas
body: <p>I have a geopandas dataframe with a geom field that retains heterogeneous shapely data types.
  I want to group them by type (e.g. shapely.geometry.Point, shapely.geometry.Polygon, shapely.geometry.MultiPolygon, etc.). This task would be accomplished via something like this:</p>
  
  <pre><code>main_gdf_clean['geometry'].groupby(by=shapely.geometry.Point)
  </code></pre>
  
  <p>Is there a workable way to accomplish what I am describing?</p>