code: def _identify(self, dataframe):
          
          path = Path(self.vert)
          idx = path.contains_points(dataframe.filter(self.channels))
  
          if self.region == 'out':
              idx = ~idx
  
          return idx
docs: Returns a list of indexes containing only the points that pass the filter.
  
          Parameters
          ----------
          dataframe : DataFrame