code: def apply_mtd(self, mtd, *args, cont=False, tag=None, **kwargs):
          
          new_lhs = getattr(self.lhs, mtd)(*args, **kwargs)
          if new_lhs == self.lhs and cont:
              new_lhs = None
          new_rhs = getattr(self.rhs, mtd)(*args, **kwargs)
          new_tag = tag
          return self._update(new_lhs, new_rhs, new_tag, cont)
docs: Call the method `mtd` on both sides of the equation
  
          That is, the left-hand-side and right-hand-side are replaced by::
  
              lhs=lhs.<mtd>(*args, **kwargs)
              rhs=rhs.<mtd>(*args, **kwargs)
  
          The `cont` and `tag` parameters are as in :meth:`apply`.