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: _validation_exception_detail.rs
    path of file: ./repos/aws-sdk-rust/sdk/costoptimizationhub/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 input failed to meet the constraints specified by the Amazon Web Services service in a specified field.</p>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq, ::std::fmt::Debug)]
pub struct ValidationExceptionDetail {
    /// <p>The field name where the invalid entry was detected.</p>
    pub field_name: ::std::string::String,
    /// <p>A message with the reason for the validation e
    
    pub fn build(self) -> ::std::result::Result<crate::types::ValidationExceptionDetail, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::ValidationExceptionDetail {
            field_name: self.field_name.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "field_name",
                    "field_name was not specified but it is required when building ValidationExceptionDetail",
                )
            })?,
            message: self.message.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "message",
                    "message was not specified but it is required when building ValidationExceptionDetail",
                )
            })?,
        })
    }