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: _s3_reference_data_source.rs
    path of file: ./repos/aws-sdk-rust/sdk/kinesisanalytics/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>Identifies the S3 bucket and object that contains the reference data. Also identifies the IAM role Amazon Kinesis Analytics can assume to read this object on your behalf.</p>
/// <p>An Amazon Kinesis Analytics application loads reference data only once. If the data changes, you call the <a href="https://docs.aws.amazon.com/kinesisanalytics/latest/dev/API_UpdateApplication.html">UpdateApplication</a> operation to trigger reloading of data into your application.</p>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq, ::std::fmt::Debug)]
pub st
    
    pub fn build(self) -> ::std::result::Result<crate::types::S3ReferenceDataSource, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::S3ReferenceDataSource {
            bucket_arn: self.bucket_arn.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "bucket_arn",
                    "bucket_arn was not specified but it is required when building S3ReferenceDataSource",
                )
            })?,
            file_key: self.file_key.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "file_key",
                    "file_key was not specified but it is required when building S3ReferenceDataSource",
                )
            })?,
            reference_role_arn: self.reference_role_arn.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "reference_role_arn",
                    "reference_role_arn was not specified but it is required when building S3ReferenceDataSource",
                )
            })?,
        })
    }