code: def evalSymbReg(individual):
      # Transform the tree expression in a callable function
      func = toolbox.compile(individual)
      # Evaluate the sum of squared difference between the expression
      # and the real function : x**4 + x**3 + x**2 + x
      values = (x / 10.0 for x in range(-10, 10))
      diff_func = (
          lambda x: (func(x) - (x**4 + x**3 + x**2 + x)) ** 2
      )
      diff = sum(map(diff_func, values))
      return (diff,)
  
file_path: deap/examples/gp/adf_symbreg.py
imports: import random
  import operator
  import math
  import numpy
  from functools import partial
  from deap import base
  from deap import creator
  from deap import gp
  from deap import tools
label_desc: Use image node_id 2 for calling a global function with example usage: evalSymbReg(individual) and returns: diff