The error is occurring when I'm running this code.

@api.multi
def action_invoice_open(self):
    res = super(AccountInvoice, self).action_invoice_open()
    destination_location = self.env('res.partner').search([('name', '=',
                                                            self.partner_id.id)]).property_stock_customer
    # self.operationn_type = self.env['ir.model.data'].xmlid_to_res_id('stock.picking_type_out')
    operation_type = self.env('stock.picking.type').search([('code', '=', 'outgoing')]).name
    source_location = self.env('stock.picking.type').search([('code', '=', 'outgoing')]).default_location_src_id

    self.env['stock.picking'].create({
        'partner_id': self.partner_id.id,
        'location_id': source_location.id,
        'location_dest_id': destination_location.id,
        'picking_type_id': operation_type.id,
    })
    return res

This was the error log


Error:
Odoo Server Error

Traceback (most recent call last):
  File "/home/mypc/Desktop/odoo-12.0/odoo/http.py", line 656, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/home/mypc/Desktop/odoo-12.0/odoo/http.py", line 314, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/home/mypc/Desktop/odoo-12.0/odoo/tools/pycompat.py", line 87, in reraise
    raise value
  File "/home/mypc/Desktop/odoo-12.0/odoo/http.py", line 698, in dispatch
    result = self._call_function(**self.params)
  File "/home/mypc/Desktop/odoo-12.0/odoo/http.py", line 346, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/home/mypc/Desktop/odoo-12.0/odoo/service/model.py", line 97, in wrapper
    return f(dbname, *args, **kwargs)
  File "/home/mypc/Desktop/odoo-12.0/odoo/http.py", line 339, in checked_call
    result = self.endpoint(*a, **kw)
  File "/home/mypc/Desktop/odoo-12.0/odoo/http.py", line 941, in __call__
    return self.method(*args, **kw)
  File "/home/mypc/Desktop/odoo-12.0/odoo/http.py", line 519, in response_wrap
    response = f(*args, **kw)
  File "/home/mypc/Desktop/odoo-12.0/addons/web/controllers/main.py", line 966, in call_button
    action = self._call_kw(model, method, args, {})
  File "/home/mypc/Desktop/odoo-12.0/addons/web/controllers/main.py", line 954, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/home/mypc/Desktop/odoo-12.0/odoo/api.py", line 759, in call_kw
    return _call_kw_multi(method, model, args, kwargs)
  File "/home/mypc/Desktop/odoo-12.0/odoo/api.py", line 746, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/home/mypc/Desktop/odoo-12.0/custom_addons/custom_contacts_field/models/custom_invoice.py", line 24, in action_invoice_open
    destination_location = self.env('res.partner').search([('name', '=',
  File "/home/mypc/Desktop/odoo-12.0/odoo/api.py", line 860, in __call__
    return Environment(cr, uid, context)
  File "/home/mypc/Desktop/odoo-12.0/odoo/api.py", line 812, in __new__
    self.registry = Registry(cr.dbname)
AttributeError: 'str' object has no attribute 'dbname'​