class AccountInvoice(models.Model):

_inherit = "account.invoice"

refund_count = fields.Integer(compute='_refund_no', string='Refund')

@api.one

@api.depends('refund_count')

def _refund_no(self):

for all in self.env['account.invoice'].search([('refund_invoice_id','=',self.id)]):

self.refund_count=len(all)

@api.multi

def action_view_refund(self):

return {

'name': _('Refund Invoice'),

'view_mode': 'form',

'view_id': self.env.ref('account.invoice_form').id,

'res_model': 'account.invoice',

'context': "{'type':'out_refund'}",

'type': 'ir.actions.act_window',

'res_id': self.refund_invoice_id,

}

view----------

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

<field name="name">sale.order.form.inherit.refund</field>

<field name="model">account.invoice</field>

<field name="inherit_id" ref="account.invoice_form"/>

<field name="arch" type="xml">

<xpath expr="//field[@name='number']" position="after">

<div class="oe_right oe_button_box">

<button name="action_view_refund" type="object" class="oe_stat_button" icon="fa-pencil-square-o" attrs="{'invisible': [('refund_count', '=', 0)]}">

<field name="refund_count" widget="statinfo" string="Refund" />

</button>

</div>

</xpath>

</field>

</record>

when i try this iam getting error like.......

raise TypeError(repr(o) + " is not JSON serializable")
TypeError: account.invoice() is not JSON serializable