problem with chained validators

Hello.

I have the following snippet:

http://arag0rn.pastebin.pl/3215

Basically, I'm trying to force user to fill other1_name field if
other1 is set to True (same for other2 and other3, respectively).

However, validation never reaches chained validators despite
validate_partial_form set to True. I'm sure I'm missing something
obvious, because similar example is in the docs, to quote
http://formencode.org/Validator.html#writing-your-own-validator

"Or you can put it in chained_validators and it will be run after the
schema. If the schema fails (the values are invalid) then
ValidateState will not be run, unless you set validate_partial_form to
True (like ValidateState = SimpleFormValidator(validate_state,
validate_partial_form=True). If you validate a partial form you should
be careful that you handle missing keys and other possibly-invalid
values gracefully."

Could someone put me on the right track?

Thank you for your time

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