ValueError: "invoice_validate() takes at least 4 arguments (4 given)" while evaluating
u'invoice_validate()'

from openerp import models, fields, api

class invoice_edits(models.Model):

    _inherit = 'account.invoice'
    state_bool = fields.Boolean(string='Active Tax', default=True)



    def invoice_validate(self, cr, uid, vals, context=None):
        if context is None:
            context = {}
        if vals.get('state_bool') == True:
             vals['number'] = self.pool.get('ir.sequence').get(cr, uid, 'sequence_sale_tax') or '/'
        if vals.get('state_bool') == False:
             vals['number'] = self.pool.get('ir.sequence').get(cr, uid, 'sequence_sale_without_tax') or '/'
        res = super(invoice_edits, self).invoice_validate(cr, uid, vals, context=context)
        return res



invoice_edits()

<openerp>
    <data>

        <record model="ir.ui.view" id="net2do_invoice_edits_form_inherit">

            <field name="name">account.invoice.form</field>
            <field name="model">account.invoice</field>
            <field name="inherit_id" ref="account.invoice_form"/>
            <field name="arch" type="xml">
                <data>
                    <xpath expr="//field[@name='account_id']" position="after">
                        <field name="state_bool" attrs="{'readonly': [('state', '=', 'open')]}"/>
                    </xpath>
                </data>
            </field>
        </record>
    </data>
</openerp>

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data noupdate="1">

<record id="sequence_sale_tax" model="ir.sequence">
            <field name="name">Account Tax</field>
            <field eval="1" name="padding"/>
            <field name="prefix">SAJ/%(year)s/</field>
        </record>

<record id="sequence_sale_without_tax" model="ir.sequence">
            <field name="name">Account Default Sales Journal</field>
            <field eval="1" name="padding"/>
            <field name="prefix">JAS/%(year)s/</field>
        </record>
        </data>
</openerp>