code: def _rectangular(n):
      """Checks to see if a 2D list is a valid 2D matrix"""
      for i in n:
          if len(i) != len(n[0]):
              return False
      return True
  
file_path: mxboard/python/mxboard/utils.py
imports: from __future__ import absolute_import
  import os
  import logging
  import numpy
  from mxnet.ndarray import NDArray, op
  from mxnet.ndarray import ndarray
  from mxnet.context import current_context
label_desc: Use image node_id 1 for calling a global function with example usage: _rectangular(n) and returns: True, False