def METHOD_NAME(self, key: str, default=None):
    """Convenience method for getting specified header from the shareable.
    Args:
        key: name of the header
        default: default value if the header doesn't exist
    Returns: value of the header if it exists in the shareable; or the specified default if it doesn't.
    """
    if not self.shareable:
        return default
    return self.shareable.get_header(key, default)