I propose the below fix:

```
    def unbind(self, sequence, funcid=None):
        """Unbind for this widget for event SEQUENCE  the
        function identified with FUNCID."""
        bound = ''
        if funcid:
            self.deletecommand(funcid)
            funcs = self.tk.call('bind', self._w, sequence, None).split('\n')
            bound = '\n'.join([f for f in funcs if not f.startswith('if {{"[{0}'.format(funcid))])
        self.tk.call('bind', self._w, sequence, bound)
```