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: _dnis_emergency_calling_configuration.rs
    path of file: ./repos/aws-sdk-rust/sdk/chimesdkvoice/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 Dialed Number Identification Service (DNIS) emergency calling configuration details associated with an Amazon Chime SDK Voice Connector's emergency calling configuration.</p>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq)]
pub struct DnisEmergencyCallingConfiguration {
    /// <p>The DNIS phone number that you route emergency calls to, in E.164 format.</p>
    pub emergency_phone_number: ::std::string::String,
    /// <p>The DNIS phone number for routing test emergency calls to, in E.164 format.</p>
    pub test_phone_number: ::std::option::Option<::std::string::String>,
    /// <p>The country from which emergency calls are allowed, in ISO 3166-1 alpha-2 format.</p>
    pub calling_country: ::std::string::String,
}
impl 
    
    pub fn build(self) -> ::std::result::Result<crate::types::DnisEmergencyCallingConfiguration, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::DnisEmergencyCallingConfiguration {
            emergency_phone_number: self.emergency_phone_number.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "emergency_phone_number",
                    "emergency_phone_number was not specified but it is required when building DnisEmergencyCallingConfiguration",
                )
            })?,
            test_phone_number: self.test_phone_number,
            calling_country: self.calling_country.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "calling_country",
                    "calling_country was not specified but it is required when building DnisEmergencyCallingConfiguration",
                )
            })?,
        })
    }