code: def diff(self, periods=1, axis=0):
          
          axis = self._get_axis_number(axis)
          return self.__constructor__(
              query_compiler=self._query_compiler.diff(periods=periods, axis=axis)
          )
docs: Finds the difference between elements on the axis requested
  
          Args:
              periods: Periods to shift for forming difference
              axis: Take difference over rows or columns
  
          Returns:
              DataFrame with the diff applied