code: def _set_item(self, key, value):
          
  
          self._ensure_valid_index(value)
          value = self._sanitize_column(key, value)
          NDFrame._set_item(self, key, value)
  
          # check if we are modifying a copy
          # try to set first as we want an invalid
          # value exception to occur first
          if len(self):
              self._check_setitem_copy()
docs: Add series to DataFrame in specified column.
  
          If series is a numpy-array (not a Series/TimeSeries), it must be the
          same length as the DataFrames index or an error will be thrown.
  
          Series/TimeSeries will be conformed to the DataFrames index to
          ensure homogeneity.