code: def fetch_processed_single_clause(element: "ClauseElement",
                                    compiler: "SQLCompiler") -> str:
      
      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)
docs: Takes a clause element that must have a single clause, and converts it
      to raw SQL text.