Saves current user credentials to user directory.

        Args:
            config_loc (str, optional): Location where credentials are to be
                stored. If no argument is provided, it will be send to the
                default location.

        Example:

            .. code::

                from cartoframes import Credentials
                creds = Credentials(username='eschbacher', key='abcdefg')
                creds.save()  # save to default location

def save(self, config_loc=None):
        """Saves current user credentials to user directory.

        Args:
            config_loc (str, optional): Location where credentials are to be
                stored. If no argument is provided, it will be send to the
                default location.

        Example:

            .. code::

                from cartoframes import Credentials
                creds = Credentials(username='eschbacher', key='abcdefg')
                creds.save()  # save to default location

        """
        if not os.path.exists(_USER_CONFIG_DIR):
            """create directory if not exists"""
            os.makedirs(_USER_CONFIG_DIR)
        with open(_DEFAULT_PATH, 'w') as f:
            json.dump({'key': self._key, 'base_url': self._base_url,
                       'username': self._username}, f)