code: def concat(self, axis, other, **kwargs):
          
          return self._append_list_of_managers(other, axis, **kwargs)
docs: Concatenates two objects together.
  
          Args:
              axis: The axis index object to join (0 for columns, 1 for index).
              other: The other_index to concat with.
  
          Returns:
              Concatenated objects.