'Initialize the AvailableAddOnExtensionInstance
:returns: twilio.rest.preview.marketplace.available_add_on.available_add_on_extension.AvailableAddOnExtensionInstance
:rtype: twilio.rest.preview.marketplace.available_add_on.available_add_on_extension.AvailableAddOnExtensionInstance'

def __init__(self, version, payload, available_add_on_sid, sid=None):

    super(AvailableAddOnExtensionInstance, self).__init__(version)
    self._properties = {'sid': payload['sid'], 'available_add_on_sid': payload['available_add_on_sid'], 'friendly_name': payload['friendly_name'], 'product_name': payload['product_name'], 'unique_name': payload['unique_name'], 'url': payload['url']}
    self._context = None
    self._solution = {'available_add_on_sid': available_add_on_sid, 'sid': (sid or self._properties['sid'])}
