@classmethod
def bind(cls, ns, location=None):
    """
        Bind a namespace to a schema location (URI).

        This is used for imports that do not specify a schemaLocation.

        @param ns: A namespace-uri.
        @type ns: str
        @param location: The (optional) schema location for the namespace.
            (default=ns)
        @type location: str

        """
    if location is None:
        location = ns
    cls.locations[ns] = location
