code: def _preprocess(self, img, trimap=None):
      data = {}
      data["img"] = img
      if trimap is not None:
          data["trimap"] = trimap
          data["gt_fields"] = ["trimap"]
      data = self.cfg.transforms(data)
      return data
  
imports: import argparse
  import codecs
  import os
  import sys
  import cv2
  import tqdm
  import yaml
  import numpy
  import paddle
  from paddle.inference import create_predictor, PrecisionType
  from paddle.inference import Config
  from paddleseg.cvlibs import manager
  from paddleseg.utils import get_sys_env, logger
  import ppmatting.transforms
  from ppmatting.utils import get_image_list, mkdir, estimate_foreground_ml, VideoReader, VideoWriter
label_desc: Use image node_id 6 for calling the Predictor obj's underlying member method code with example usage: obj._preprocess(img, trimap) and returns: data