def get_user_agent(module: Optional[str] = None) -> str:
    r"""
    Returns a custom user agent header.

    Args:
        module (Optional[str]):
            Optional. The module for a custom user agent header.

    Returns:
        Tuple[str, str]

    """
    try:
        llama_index_version = metadata.version("llama-index")
    except metadata.PackageNotFoundError:
        llama_index_version = "0.0.0"
    client_library_version = (
        f"{llama_index_version}-{module}" if module else llama_index_version
    )
    return f"llama-index/{client_library_version}"

    Returns a custom user agent header.

    Args:
        module (Optional[str]):
            Optional. The module for a custom user agent header.

    Returns:
        Tuple[str, str]

    
llama-index-integrations/indices/llama-index-indices-managed-vertexai/llama_index/indices/managed/vertexai/base.py