self.write(" -> ")
            self.dispatch(t.returns)
        self.enter()
        self.dispatch(t.body)
        self.leave()
    def _For(self, t):
        self.__For_helper("for ", t)
    def _AsyncFor(self, t):
        self.__For_helper("async for ", t)
    def __For_helper(self, fill, t):
        self.fill(fill)
        self.dispatch(t.target)
        self.write(" in ")
        self.dispatch(t.iter)
        self.enter()
        self.dispatch(t.body)
        self.leave()
        if t.orelse:
            self.fill("else")
            self.enter()
            self.dispatch(t.orelse)
            self.leave()
    def _If(self, t):
        self.fill("if ")
        self.dispatch(t.test)
        self.enter()
        self.dispatch(t.body)
        self.leave()
        # collapse nested ifs into equivalent elifs.
        while t.orelse and len(t.orelse) == 1 and isinstance(t.orelse[0], ast.If):
            t = t.orelse[0]
            self.fill("elif ")
            self.dispatch(t.test)
            self.enter()
            self.dispatch(t.body)
            self.leave()
        # final else
        if t.orelse:
            self.fill("else")
            self.enter()
            self.dispatch(t.orelse)
            self.leave()
    def _While(self, t):
        self.fill("while ")
        self.dispatch(t.test)
        self.enter()
        self.dispatch(t.body)
        self.leave()
        if t.orelse:
            self.fill("else")
            self.enter()
            self.dispatch(t.orelse)
            self.leave()