code: def rename_axis(self, mapper, axis, copy=True, level=None):
          
          obj = self.copy(deep=copy)
          obj.set_axis(axis, _transform_index(self.axes[axis], mapper, level))
          return obj
docs: Rename one of axes.
  
          Parameters
          ----------
          mapper : unary callable
          axis : int
          copy : boolean, default True
          level : int, default None