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: _email_field.rs
    path of file: ./repos/aws-sdk-rust/sdk/wafv2/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 name of the field in the request payload that contains your customer's email.</p>
/// <p>This data type is used in the <code>RequestInspectionACFP</code> data type.</p>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq, ::std::fmt::Debug)]
pub struct EmailField {
    /// <p>The name of the email field.</p>
    /// <p>How you specify this d
    
    pub fn build(self) -> ::std::result::Result<crate::types::EmailField, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::EmailField {
            identifier: self.identifier.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "identifier",
                    "identifier was not specified but it is required when building EmailField",
                )
            })?,
        })
    }