add a tag or tags to a symbol
        
        Parameters
        ----------
        tags : str or [str,]
            Tags to be added

def add_tags(self, tags):
        """ add a tag or tags to a symbol
        
        Parameters
        ----------
        tags : str or [str,]
            Tags to be added
        """
        # SQLA Adding a SymbolTag object, feels awkward/uneccessary.
        # Should I be implementing this functionality a different way?

        if isinstance(tags, (str, unicode)):
            tags = [tags]

        objs = object_session(self)
        tmps = [SymbolTag(tag=t, sym=self) for t in tags]
        objs.add_all(tmps)
        objs.commit()