def find_signature(self, signature_id=None, signer_email_address=None):
if self.signatures:<EOL><INDENT>for signature in self.signatures:<EOL><INDENT>if signature.signature_id == signature_id or signature.signer_email_address == signer_email_address: <EOL><INDENT>return signature<EOL><DEDENT><DEDENT><DEDENT>
Return a signature for the given parameters

            Args:

                signature_id (str):             Id of the signature to retrieve.
                signer_email_address (str):     Email address of the associated signer for the signature to retrieve.

            Returns:
                A Signature object or None