def update(self, friendly_name=values.unset, certificate=values.unset,<EOL>private_key=values.unset, sandbox=values.unset, api_key=values.unset,<EOL>secret=values.unset):
data = values.of({<EOL>'<STR_LIT>': friendly_name,<EOL>'<STR_LIT>': certificate,<EOL>'<STR_LIT>': private_key,<EOL>'<STR_LIT>': sandbox,<EOL>'<STR_LIT>': api_key,<EOL>'<STR_LIT>': secret,<EOL>})<EOL>payload = self._version.update(<EOL>'<STR_LIT:POST>',<EOL>self._uri,<EOL>data=data,<EOL>)<EOL>return CredentialInstance(self._version, payload, sid=self._solution['<STR_LIT>'], )<EOL>
Update the CredentialInstance

:param unicode friendly_name: A string to describe the resource
:param unicode certificate: [APN only] The URL encoded representation of the certificate
:param unicode private_key: [APN only] The URL encoded representation of the private key
:param bool sandbox: [APN only] Whether to send the credential to sandbox APNs
:param unicode api_key: [GCM only] The API key for the project that was obtained from the Google Developer console for your GCM Service application credential
:param unicode secret: [FCM only] The Server key of your project from Firebase console

:returns: Updated CredentialInstance
:rtype: twilio.rest.chat.v2.credential.CredentialInstance