In odoo development, how to import classes from one module to another module

By extending the ir.qweb class in odoo/addons/base/ir , to extend and implement custom functions, the copy class structure is as follows:

 

# -*- coding: utf-8 -*-
import ast
from urlparse import urlparse
from lxml import html

from .qweb import QWeb, Contextifier
from .assetsbundle import AssetsBundle
from lxml import etree
from collections import OrderedDict

from odoo import api, models, tools
from odoo.tools.safe_eval import assert_valid_codeobj, _BUILTINS, _SAFE_OPCODES
from odoo.http import request
from odoo.modules.module import get_resource_path
import json
from time import time

import logging
_logger = logging.getLogger(__name__)


class IrQWebCF(models.AbstractModel, QWeb):
    '''
    Inherit the ir.qweb class to realize the rendering output of custom attributes
    '''
    _name = 'ir.qweb'
    _inherit = 'ir.qweb'

    def _get_field(self, record, field_name, expression, tagName, field_options, options, values):
        field = record._fields[field_name]

        field_options['tagName'] = tagName
        field_options['expression'] = expression
        field_options['type'] = field_options.get('widget', field.type)
        inherit_branding = options.get('inherit_branding',
                                       options.get('inherit_branding_auto') and record.check_access_rights('write', False))
        field_options['inherit_branding'] = inherit_branding
        translate = options.get('edit_translations') and options.get('translatable') and field.translate
        field_options['translate'] = translate

        # field converter
        model = 'ir.qweb.field.' + field_options['type']
        converter = self.env[model] if model in self.env else self.env['ir.qweb.field']

        # get content
        content = converter.record_to_html(record, field_name, field_options)
        attributes = converter.attributes(record, field_name, field_options, values)

        return (attributes, content, inherit_branding or translate)

 At runtime, it will report that QWeb, Contextifier, and AssetsBundlecannot be imported. Just change it to the following.

 

 

# -*- coding: utf-8 -*-
import ast
from urlparse import urlparse
from lxml import html

#### The next two lines
#from .qweb import QWeb, Contextifier
#from .assetsbundle import AssetsBundle
### Change to
from odoo.addons.base.ir.ir_qweb.qweb import QWeb, Contextifier
from odoo.addons.base.ir.ir_qweb.assetsbundle import AssetsBundle