code: # -*- coding: utf-8 -*-
  """
      utils
      ~~~~~
  """
  import numpy as np
  
  
  def sizes_to_indices(sizes):
      """Converting sizes to corresponding indices.
      Args:
          sizes (numpy.dnarray):
              An array consist of non-negative number.
      Returns:
          list{range}:
              List the indices.
      """
      u_id = np.cumsum(sizes)
      l_id = np.insert(u_id[:-1], 0, 0)
  
      return [
          np.arange(l, u) for l, u in zip(l_id, u_id)
      ]
  
apis: numpy.arange numpy.cumsum numpy.insert