def lookupProcedure(self, procedureName):
        """
        Lookup a procedure from a fixed set of choices, either I{echo} or
        I{system.listeMethods}.
        """
        if procedureName == 'echo':
            return self.echo
        raise xmlrpc.NoSuchFunction(
            self.NOT_FOUND, 'procedure %s not found' % (procedureName,))

        Lookup a procedure from a fixed set of choices, either I{echo} or
        I{system.listeMethods}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_xmlrpc.py