def expect_keyword(parser, value):
    # type: (Parser, str) -> Token
    """If the next token is a keyword with the given value, return that
    token after advancing the parser. Otherwise, do not change the parser
    state and return False."""
    token = parser.token
    if token.kind == TokenKind.NAME and token.value == value:
        advance(parser)
        return token

    raise GraphQLSyntaxError(
        parser.source,
        token.start,
        u'Expected "{}", found {}'.format(value, get_token_desc(token)),
    )
If the next token is a keyword with the given value, return that
    token after advancing the parser. Otherwise, do not change the parser
    state and return False.