docs: def add_alias(self, alias):
          """ Add an alias to a Symbol
          
          Parameters
          ----------
          alias : str
              The alias
          """
          objs = object_session(self)
          
          if isinstance(alias, list):
              raise NotImplementedError
          elif isinstanceofany(alias, (str, unicode)):
              a = SymbolAlias(self, alias)
              self.aliases.append(a)
              objs.add(a)