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: _add_on_request.rs
    path of file: ./repos/aws-sdk-rust/sdk/lightsail/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>Describes a request to enable, modify, or disable an add-on for an Amazon Lightsail resource.</p><note>
/// <p>An additional cost may be associated with enabling add-ons. For more information, see the <a href="https://aws.amazon.com/lightsail/pricing/">Lightsail pricing page</a>.</p>
/// </note>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq, ::std::fmt::Debug)]
pub struct AddOnReques
    
    pub fn build(self) -> ::std::result::Result<crate::types::AddOnRequest, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::AddOnRequest {
            add_on_type: self.add_on_type.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "add_on_type",
                    "add_on_type was not specified but it is required when building AddOnRequest",
                )
            })?,
            auto_snapshot_add_on_request: self.auto_snapshot_add_on_request,
            stop_instance_on_idle_request: self.stop_instance_on_idle_request,
        })
    }