You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: _notification_channel.rs
    path of file: ./repos/aws-sdk-rust/sdk/rekognition/src/types
    
    the code of the file until where you have to start completion: // Code generated by software.amazon.smithy.rust.codegen.smithy-rs. DO NOT EDIT.

/// <p>The Amazon Simple Notification Service topic to which Amazon Rekognition publishes the completion status of a video analysis operation. For more information, see <a href="https://docs.aws.amazon.com/rekognition/latest/dg/api-video.html">Calling Amazon Rekognition Video operations</a>. Note that the Amazon SNS topic must have a topic name that begins with <i>AmazonRekognition</i> if you are using the A
    
    pub fn build(self) -> ::std::result::Result<crate::types::NotificationChannel, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::NotificationChannel {
            sns_topic_arn: self.sns_topic_arn.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "sns_topic_arn",
                    "sns_topic_arn was not specified but it is required when building NotificationChannel",
                )
            })?,
            role_arn: self.role_arn.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "role_arn",
                    "role_arn was not specified but it is required when building NotificationChannel",
                )
            })?,
        })
    }