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

    Parameters
    ----------
    line_str : str
        Target line string. e.g., 'price : int'

    Returns
    -------
    return_value_name : str
        Return value name. If colon character not exists in
        line string, a blank string will be set.
    """
    colon_exists: bool = ':' in line_str
    if colon_exists:
        return_value_name: str = line_str.split(':')[0]
    else:
        return_value_name = ''
    return_value_name = return_value_name.strip()
    return return_value_name