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: _list_sol_network_package_metadata.rs
    path of file: ./repos/aws-sdk-rust/sdk/tnb/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>Metadata related to a network package.</p>
/// <p>A network package is a .zip file in CSAR (Cloud Service Archive) format defines the function packages you want to deploy and the Amazon Web Services infrastructure you want to deploy them on.</p>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq, ::std::fmt::Debug)]
pub struct ListSolNetworkPackageMetadata {
    /// <p>The date that the resource was 
    
    pub fn build(self) -> ::std::result::Result<crate::types::ListSolNetworkPackageMetadata, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::ListSolNetworkPackageMetadata {
            created_at: self.created_at.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "created_at",
                    "created_at was not specified but it is required when building ListSolNetworkPackageMetadata",
                )
            })?,
            last_modified: self.last_modified.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "last_modified",
                    "last_modified was not specified but it is required when building ListSolNetworkPackageMetadata",
                )
            })?,
        })
    }