Deserialize a Namespace object.

    :param data: bytes or str
    :return: namespace

def deserialize_namespace(data):
    ''' Deserialize a Namespace object.

    :param data: bytes or str
    :return: namespace
    '''
    if isinstance(data, bytes):
        data = data.decode('utf-8')
    kvs = data.split()
    uri_to_prefix = {}
    for kv in kvs:
        i = kv.rfind(':')
        if i == -1:
            raise ValueError('no colon in namespace '
                             'field {}'.format(repr(kv)))
        uri, prefix = kv[0:i], kv[i + 1:]
        if not is_valid_schema_uri(uri):
            # Currently this can't happen because the only invalid URIs
            # are those which contain a space
            raise ValueError(
                'invalid URI {} in namespace '
                'field {}'.format(repr(uri), repr(kv)))
        if not is_valid_prefix(prefix):
            raise ValueError(
                'invalid prefix {} in namespace field'
                ' {}'.format(repr(prefix), repr(kv)))
        if uri in uri_to_prefix:
            raise ValueError(
                'duplicate URI {} in '
                'namespace {}'.format(repr(uri), repr(data)))
        uri_to_prefix[uri] = prefix
    return Namespace(uri_to_prefix)