'Create an AuthRequest object for the specified
service_endpoint. This method will create an association if
necessary.'

def begin(self, service_endpoint):

    if (self.store is None):
        assoc = None
    else:
        assoc = self._getAssociation(service_endpoint)
    request = AuthRequest(service_endpoint, assoc)
    request.return_to_args[self.openid1_nonce_query_arg_name] = mkNonce()
    if request.message.isOpenID1():
        request.return_to_args[self.openid1_return_to_identifier_name] = request.endpoint.claimed_id
    return request
