Constructs and returns the Lambda Permission resource allowing the Authorizer to invoke the function.

        :returns: the permission resource
        :rtype: model.lambda_.LambdaPermission

def _get_permission(self, authorizer_name, authorizer_lambda_function_arn):
        """Constructs and returns the Lambda Permission resource allowing the Authorizer to invoke the function.

        :returns: the permission resource
        :rtype: model.lambda_.LambdaPermission
        """
        rest_api = ApiGatewayRestApi(self.logical_id, depends_on=self.depends_on, attributes=self.resource_attributes)
        api_id = rest_api.get_runtime_attr('rest_api_id')

        partition = ArnGenerator.get_partition_name()
        resource = '${__ApiId__}/authorizers/*'
        source_arn = fnSub(ArnGenerator.generate_arn(partition=partition, service='execute-api', resource=resource),
                           {"__ApiId__": api_id})

        lambda_permission = LambdaPermission(self.logical_id + authorizer_name + 'AuthorizerPermission',
                                             attributes=self.passthrough_resource_attributes)
        lambda_permission.Action = 'lambda:invokeFunction'
        lambda_permission.FunctionName = authorizer_lambda_function_arn
        lambda_permission.Principal = 'apigateway.amazonaws.com'
        lambda_permission.SourceArn = source_arn

        return lambda_permission