def fetch_processed_single_clause(element: "ClauseElement",
                                  compiler: "SQLCompiler") -> str:
    """
    Takes a clause element that must have a single clause, and converts it
    to raw SQL text.
    """
    if len(element.clauses) != 1:
        raise TypeError("Only one argument supported; {} were passed".format(
            len(element.clauses)))
    clauselist = element.clauses  # type: ClauseList
    first = clauselist.get_children()[0]
    return compiler.process(first)
Takes a clause element that must have a single clause, and converts it
    to raw SQL text.