class_docstr: Object which carries out genetic search and returns top performing model
  upon completion.
code: def _mutate(self, genome, generation):
      # increase mutations as program continues
      num_mutations = max(3, generation // 4)
      return self.genome_handler.mutate(genome, num_mutations)
  
imports: from __future__ import print_function
  import random
  import csv
  import operator
  import gc
  import os
  from datetime import datetime
  from keras.callbacks import EarlyStopping
  from keras.models import load_model
  import keras.backend
  from sklearn.metrics import log_loss
  import numpy
label_desc: Use image node_id 13 for calling the DEvol obj's underlying member method code with example usage: obj._mutate(genome, generation) and returns: self