if d:
                self.write("=")
                self.traverse(d)
            if index == len(node.posonlyargs):
                self.write(", /")
        # varargs, or bare '*' if no varargs but keyword-only arguments present
        if node.vararg or node.kwonlyargs:
            if first:
                first = False
            else:
                self.write(", ")
            self.write("*")
            if node.vararg:
                self.write(node.vararg.arg)
                if node.vararg.annotation:
                    self.write(": ")
                    self.traverse(node.vararg.annotation)
        # keyword-only arguments
        if node.kwonlyargs:
            for a, d in zip(node.kwonlyargs, node.kw_defaults):
                self.write(", ")
                self.traverse(a)
                if d:
                    self.write("=")
                    self.traverse(d)
        # kwargs
        if node.kwarg:
            if first:
                first = False
            else:
                self.write(", ")
            self.write("**" + node.kwarg.arg)
            if node.kwarg.annotation:
                self.write(": ")
                self.traverse(node.kwarg.annotation)
    def visit_keyword(self, node):
        if node.arg is None:
            self.write("**")
        else:
            self.write(node.arg)
            self.write("=")
        self.traverse(node.value)
    def visit_Lambda(self, node):
        with self.require_parens(_Precedence.TEST, node):
            self.write("lambda")
            with self.buffered() as buffer:
                self.traverse(node.args)
            if buffer:
                self.write(" ", *buffer)
            self.write(": ")