I have written this button which does a simple operation, but Odoo says my arguments are wrong. Its an 'object' type button. Can you help me out?

UPDATE:

Here's my code:

PY:

from openerp.osv import fields, osv

from openerp import api

import openerp.addons.decimal_precision as dp

from openerp.osv import orm

from calendar import monthrange

from datetime import datetime, timedelta

from dateutil import relativedelta

class record(orm.Model):

_name="record"

@api.multi

def button_calculate_monthly_interest(self):

print 'hello Odoo'

def button_monthly_interest(self, cr, uid, ids, context=None):

print("hi")

XML:

<button name="button_calculate_monthly_interest" string="Calculate Monthly Interest" type="object"/>

When I use the old API, I get AttributeError: 'record' object has no attribute 'button_monthly_interest'

When I use new API, I get the error: 1 exact field expected, 5 given.