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: _lambda_function_associations.rs
    path of file: ./repos/aws-sdk-rust/sdk/cloudfront/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>A complex type that specifies a list of Lambda@Edge functions associations for a cache behavior.</p>
/// <p>If you want to invoke one or more Lambda@Edge functions triggered by requests that match the <code>PathPattern</code> of the cache behavior, specify the applicable values for <code>Quantity</code> and <code>Items</code>. Note that there can be up to 4 <code>LambdaFunctionAssociation</code> items 
    
    pub fn build(self) -> ::std::result::Result<crate::types::LambdaFunctionAssociations, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::LambdaFunctionAssociations {
            quantity: self.quantity.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "quantity",
                    "quantity was not specified but it is required when building LambdaFunctionAssociations",
                )
            })?,
            items: self.items,
        })
    }