def resolveport(self, definitions):
        """
        Resolve port_type reference.
        @param definitions: A definitions object.
        @type definitions: L{Definitions}
        """
        ref = qualify(self.type, self.root, definitions.tns)
        port_type = definitions.port_types.get(ref)
        if port_type is None:
            raise Exception("portType '%s', not-found" % self.type)
        else:
            self.type = port_type