def _convert_yaml_to_bool(_yaml_bool_value):
    """This function converts the 'yes' and 'no' YAML values to traditional Boolean values.

    .. versionchanged:: 2.5.2
       A conversion is now only attempted if the value is not already in Boolean format.
    """
    if type(_yaml_bool_value) != bool:
        true_values = ['yes', 'true']
        if _yaml_bool_value.lower() in true_values:
            _yaml_bool_value = True
        else:
            _yaml_bool_value = False
    return _yaml_bool_value
