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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def bindings(self):
 """ Access the bindings :returns: twilio.rest.chat.v2.service.binding.BindingList :rtype: twilio.rest.chat.v2.service.binding.BindingList """

        if self._bindings is None:
            self._bindings = BindingList(self._version, service_sid=self._solution['sid'], )
        return self._bindings