1..17
# ->clean()
# true values
 -  returns true if the value is in the true_values option
 -  returns true if the value is in the true_values option
 -  returns true if the value is in the true_values option
 -  returns true if the value is in the true_values option
 -  returns true if the value is in the true_values option
 -  returns true if the value is in the true_values option
# false values
 -  returns false if the value is in the false_values option
 -  returns false if the value is in the false_values option
 -  returns false if the value is in the false_values option
 -  returns false if the value is in the false_values option
 -  returns false if the value is in the false_values option
 -  returns false if the value is in the false_values option
 -  returns false if the value is null
 -  throws an error if the input value is not a true or a false value
 -  throws a sfValidatorError
# empty
 -  returns false if no value is given
 -  returns the value of the empty_value option if no value is given
# Looks like everything went fine.