def METHOD_NAME(user: JustfixUser) -> str:
    """
    Given a user, return the DocuSign client user ID representing it.
    According to the DocuSign documentation, the client user ID is:
    > An alphanumeric value that serves as an ID for the signer throughout
    > the signing process. The combination of this value, the signer's name,
    > and the signer's email is used to uniquely identify them.
    For more details, see:
    https://developers.docusign.com/esign-rest-api/code-examples/quickstart-request-signature-embedded
    """
    return str(user.pk)