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: _get_user_id_output.rs
    path of file: ./repos/aws-sdk-rust/sdk/identitystore/src/operation/get_user_id
    
    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.
#[allow(missing_docs)] // documentation missing in model
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq, ::std::fmt::Debug)]
pub struct GetUserIdOutput {
    /// <p>The identifier for a user in the identity store.</p>
    pub user_id: ::std::string::String,
    /// <p>The globally unique identifier for the identity store.</p>
    pub identity_store_id: ::std::string::String,
    _request_id: Option<String>,
}
impl GetUserIdOutput {
    /// <p>The identifier for a user in the identity store.</p>
    pub fn user_id(&self) -> &str {
        use std::ops::Deref;
        
    
    pub fn build(self) -> ::std::result::Result<crate::operation::get_user_id::GetUserIdOutput, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::operation::get_user_id::GetUserIdOutput {
            user_id: self.user_id.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "user_id",
                    "user_id was not specified but it is required when building GetUserIdOutput",
                )
            })?,
            identity_store_id: self.identity_store_id.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "identity_store_id",
                    "identity_store_id was not specified but it is required when building GetUserIdOutput",
                )
            })?,
            _request_id: self._request_id,
        })
    }