code: def argmax(self, axis=None, skipna=True):
          
          nv.validate_minmax_axis(axis)
          return nanops.nanargmax(self._values, skipna=skipna)
docs: Return an ndarray of the maximum argument indexer.
  
          Parameters
          ----------
          axis : {None}
              Dummy argument for consistency with Series
          skipna : bool, default True
  
          See Also
          --------
          numpy.ndarray.argmax