Used to create a new attribute on Sovrin
        :param attrib: attribute to add
        :return: number of pending txns

def addAttribute(self, attrib: Attribute):
        """
        Used to create a new attribute on Sovrin
        :param attrib: attribute to add
        :return: number of pending txns
        """
        self._attributes[attrib.key()] = attrib
        req = attrib.ledgerRequest()
        if req:
            self.pendRequest(req, attrib.key())
        return len(self._pending)