const query = wx.createSelectorQuery().in(_this)

                    query.select('#photo_canvas')

                        .fields({

                            node: true,

                            size: true

                        })

手机预览，控制台提示 canvas instanceof MagicBrushCanvas

是怎么回事？https://developers.weixin.qq.com/s/oSNjAsmI7UCr