def METHOD_NAME(env_name: str) -> str:
    """
    Convert an env name as stored in web.ctx.env to a "normal"
    header name
    >>> header_name_from_env('HTTP_FOO_BAR')
    'foo-bar'
    >>> header_name_from_env('CONTENT_LENGTH')
    'content-length'
    """
    header_name = env_name
    if env_name.startswith('HTTP_'):
        header_name = env_name[5:]
    return header_name.lower().replace('_', '-')