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: _session_key_amex.rs
    path of file: ./repos/aws-sdk-rust/sdk/paymentcryptographydata/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>Parameters to derive session key for an Amex payment card.</p>
#[non_exhaustive]
#[derive(::std::clone::Clone, ::std::cmp::PartialEq)]
pub struct SessionKeyAmex {
    /// <p>The Primary Account Number (PAN) of the cardholder. A PAN is a unique identifier for a payment credit or debit card and associates the card to a specific account holder.</p>
    pub primary_account_number: ::std::string::String,
    /// <p>A number that identifies and differentiates payment cards with the same Primary Account Number (PAN).</p>
    pub pan_sequence_number: ::std::string::String,
}
impl SessionKeyAmex {
    /// <p>The Primary Account Number (PAN) of the cardholder.
    
    pub fn build(self) -> ::std::result::Result<crate::types::SessionKeyAmex, ::aws_smithy_types::error::operation::BuildError> {
        ::std::result::Result::Ok(crate::types::SessionKeyAmex {
            primary_account_number: self.primary_account_number.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "primary_account_number",
                    "primary_account_number was not specified but it is required when building SessionKeyAmex",
                )
            })?,
            pan_sequence_number: self.pan_sequence_number.ok_or_else(|| {
                ::aws_smithy_types::error::operation::BuildError::missing_field(
                    "pan_sequence_number",
                    "pan_sequence_number was not specified but it is required when building SessionKeyAmex",
                )
            })?,
        })
    }