parameters: (self, key, cred)
docstring: Update a credential and write the multistore.
  
      This must be called when the multistore is locked.
  
      Args:
        key: The key used to retrieve the credential
        cred: The OAuth2Credential to update/set
docstring_summary: Update a credential and write the multistore.
docstring_tokens: Update a credential and write the multistore .
function: def _update_credential(self, key, cred):
      """Update a credential and write the multistore.
  
      This must be called when the multistore is locked.
  
      Args:
        key: The key used to retrieve the credential
        cred: The OAuth2Credential to update/set
      """
      self._data[key] = cred
      self._write()
function_tokens: def _update_credential ( self , key , cred ) : self . _data [ key ] = cred self . _write ( )