code: def reset_index(self, inplace=True, drop=True):
          
          if len(self.column_types) == 1:
              vectype = self.column_types[0]
              if isinstance(vectype, WeldVec):
                  elem_type = vectype.elemType
                  if isinstance(elem_type, WeldStruct):
                      self.column_types = elem_type.field_types
                      value_type = WeldStruct(self.column_types)
                  else:
                      self.column_types = elem_type
                      value_type = elem_type
                  if len(self.grouping_column_types) == 1:
                      group_type = self.grouping_column_types[0]
                  else:
                      group_type = WeldStruct(self.grouping_column_types)
  
                  self.weld_type = WeldStruct([group_type, value_type])
                  self.expr = grizzly_impl.flatten_group(
                      self.expr,
                      self.column_types,
                      self.grouping_column_types
                  )
docs: Flattens the grouped data structure.
  
          #TODO: The parameters here are meaningless
  
          Flattens the grouped data structure.
          What is returned is a DataFrameWeld object.