old_contents: class Neuron:
      pass
  
  class NeuronNetwork:
      neurons = []
  
new_contents: class Neuron:
      pass
  
  class NeuronNetwork:
      neurons = []
  
      def __init__(self, rows, columns):
          self.neurons = []
          for row in xrange(rows):
              self.neurons.append([])
              for column in xrange(columns):
                  self.neurons[row].append(Neuron())
  
subject: Create 2D list of Neurons in NeuronNetwork's init