Add an alias to a Symbol
        
        Parameters
        ----------
        alias : str
            The alias

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)