def _get_return_value_type_name_from_line(line_str: str) -> str:
    """
    Get the type name of return value from the target line string.

    Parameters
    ----------
    line_str : str
        Target line string.

    Returns
    ----------
    return_value_type_name : str
        Type name of return value.
    """
    colon_exists: bool = ':' in line_str
    if not colon_exists:
        return_value_type_name: str = line_str.split(':')[0]
    else:
        return_value_type_name = line_str.split(':')[1]
    return_value_type_name = return_value_type_name.strip()
    return return_value_type_name