'Update the TriggerInstance
:param unicode callback_method: HTTP method to use with callback_url
:param unicode callback_url: URL Twilio will request when the trigger fires
:param unicode friendly_name: A user-specified, human-readable name for the trigger.
:returns: Updated TriggerInstance
:rtype: twilio.rest.api.v2010.account.usage.trigger.TriggerInstance'

def update(self, callback_method=values.unset, callback_url=values.unset, friendly_name=values.unset):

    data = values.of({'CallbackMethod': callback_method, 'CallbackUrl': callback_url, 'FriendlyName': friendly_name})
    payload = self._version.update('POST', self._uri, data=data)
    return TriggerInstance(self._version, payload, account_sid=self._solution['account_sid'], sid=self._solution['sid'])
