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_source_properties.rs
    path of file: ./repos/aws-sdk-rust/sdk/appflow/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 properties that are applied when Amazon S3 is being used as the flow source.</p>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq, ::std::fmt::Debu
    
    pub fn build(self) -> ::std::result::Result<crate::types::S3SourceProperties, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::S3SourceProperties {
            bucket_name: self.bucket_name.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "bucket_name",
                    "bucket_name was not specified but it is required when building S3SourceProperties",
                )
            })?,
            bucket_prefix: self.bucket_prefix,
            s3_input_format_config: self.s3_input_format_config,
        })
    }