Edit the credentials used by the :py:class:`~pypersonalassistant.secure.secure` class.
        
        .. note :: User input is required.

        By default, unset credentials will be displayed.
        
        :param string credential: A specific credential to edit.
        :param bool already_set: If `False` will show all credentials, whether set or unset.

def edit_credentials(self, credential=None, already_set=True):
        """
        Edit the credentials used by the :py:class:`~pypersonalassistant.secure.secure` class.
        
        .. note :: User input is required.

        By default, unset credentials will be displayed.
        
        :param string credential: A specific credential to edit.
        :param bool already_set: If `False` will show all credentials, whether set or unset.
        """
        # get user input of credentials
        # save and reload credentials.json
        credentials_required = self._CREDENTIALS_REQUIRED
        if credential:
            credentials_required = [credential]
        
        for cred in credentials_required:
            # If credential is already set, decide whether to continue
            if (cred in self._credentials) and ((already_set is False) and (credential is None)):
                continue
            else:
                current_encrypted_value = ''
                try:
                    current_encrypted_value = self._credentials_encrypted[cred]
                except KeyError:
                    None
                
                prompt = '\nCredential: {0}\nCurrent (encrypted) value: {1}\nEnter new value, or press enter to skip: '.format(cred, current_encrypted_value)
                input_value = confirm_input(prompt)      
                if input_value == '':
                    logging.info('{0} skipped'.format(cred))
                else:
                    self._credentials.update({cred: input_value})
                    logging.info('{0} updated: {1}'.format(cred, input_value))
        self._save_credentials()
        self._load_credentials()