class_docstr: Class to contain ND image as list of (N-1)D images 
docstr: Length of image list
          
docstr_tok: ["Length","of","image","list"]
code: def __len__(self):
      """Length of image list"""
      return len(self.list)
  
file_path: nipy/nipy/core/image/image_list.py
imports: import warnings
  import numpy
  from ..reference.coordinate_map import AxisError, drop_io_dim, io_axis_indices
  from .image import Image, is_image, iter_axis
label_desc: Use image node_id 4 for calling the ImageList obj's underlying member method code with example usage: obj.__len__() and returns: len