module is named aikido (name of martial art)
aikidoka is person that is doing that and inherits from party

in /usr/local/lib/python2.6/dist-packages/trytond_aikido/trytond/modules/aikido I have:

::::::::::::::
aikidoka.py
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# -*- coding: utf-8 -*-
from trytond.model import ModelView, ModelSQL, fields
class Aikidoka(ModelSQL, ModelView):
    'Aikidoka'
    _name = 'party.party'
    _description = __doc__

    dateofbirth = fields.Char('Date of Birth')

Aikidoka()
::::::::::::::
__init__.py
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# -*- coding: utf-8 -*-
from party import *

from aikido import *
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__tryton__.py
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# -*- coding: utf-8 -*-
{
    'name' : 'Aikidoka',
    'version' : '0.0.1',
    'author' : 'Pander',
    'email' : 'pander@users.sourceforge.net',
    'description': 'Derived from Party with customisation for aikido',
    'depends' : [
        'ir',
        'party',
    ],
    'xml' : [
        'aikidoka.xml',
    ],
    'translation' : [
    ],
}

Is this correct so far?

How do I set up aikidoka.xml to only add a label and field to party.xml?