<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def with_subject(self, subject):
 """Create a copy of these credentials with the specified subject. Args: subject (str):
 The subject claim. Returns: google.auth.service_account.Credentials: A new credentials instance. """

        return self.__class__(
            self._signer,
            service_account_email=self._service_account_email,
            scopes=self._scopes,
            token_uri=self._token_uri,
            subject=subject,
            project_id=self._project_id,
            additional_claims=self._additional_claims.copy())