Get the attribute dict given the attribute set by the symbol.

        Parameters
        ----------
        attr : dict of string to string
            The attribute passed in by user during symbol creation.

        Returns
        -------
        attr : dict of string to string
            Updated attributes to add other scope related attributes.

def get(self, attr):
        """
        Get the attribute dict given the attribute set by the symbol.

        Parameters
        ----------
        attr : dict of string to string
            The attribute passed in by user during symbol creation.

        Returns
        -------
        attr : dict of string to string
            Updated attributes to add other scope related attributes.
        """
        if self._attr:
            ret = self._attr.copy()
            if attr:
                ret.update(attr)
            return ret
        else:
            return attr if attr else {}