class_docstr: Produce images read from a list of files as (h, w, c) arrays. 
code: def __len__(self):
      return len(self.files)
  
imports: import copy
  import numpy
  from contextlib import contextmanager
  from ..utils import logger
  from ..utils.argtools import shape2d
  from .base import RNGDataFlow
  from .common import MapData, MapDataComponent
label_desc: Use image node_id 2 for calling the ImageFromFile obj's underlying member method code with example usage: obj.__len__() and returns: len