code: def killCells(self, percent=0.05):
      
      numColumns = numpy.prod(self.getColumnDimensions())
  
      if self.zombiePermutation is None:
        self.zombiePermutation = numpy.random.permutation(numColumns)
  
      self.numDead = int(round(percent * numColumns))
  
      if self.numDead > 0:
        self.deadCols = self.zombiePermutation[0:self.numDead]
      else:
        self.deadCols = numpy.array([])
  
      self.deadColumnInputSpan = self.getConnectedSpan(self.deadCols)
      self.removeDeadColumns()
docs: Changes the percentage of cells that are now considered dead. The first
      time you call this method a permutation list is set up. Calls change the
      number of cells considered dead.