code: def test_validate_good(self):
      f = self.f
      g = self.g
  
      NumericalExpression("x_0", (f,), dtype=float64_dtype)
      NumericalExpression("x_0 ", (f,), dtype=float64_dtype)
      NumericalExpression("x_0 + x_0", (f,), dtype=float64_dtype)
      NumericalExpression("x_0 + 2", (f,), dtype=float64_dtype)
      NumericalExpression("2 * x_0", (f,), dtype=float64_dtype)
      NumericalExpression("x_0 + x_1", (f, g), dtype=float64_dtype)
      NumericalExpression(
          "x_0 + x_1 + x_0", (f, g), dtype=float64_dtype
      )
      NumericalExpression("x_0 + 1 + x_1", (f, g), dtype=float64_dtype)
  
imports: from itertools import permutations
  from operator import add, ge, gt, le, lt, methodcaller, mul, ne, sub
  from string import ascii_uppercase
  from unittest import TestCase
  import numpy
  from numpy import arange, array, eye, float64, full, isnan, zeros
  from pandas import DataFrame, date_range, Int64Index
  from catalyst.pipeline import Factor, Filter
  from catalyst.pipeline.expression import NumericalExpression, NUMEXPR_MATH_FUNCS
  from catalyst.testing import check_allclose
  from catalyst.utils.numpy_utils import datetime64ns_dtype, float64_dtype
label_desc: Use image node_id 4 for calling the NumericalExpressionTestCase obj's underlying member method code with example usage: obj.test_validate_good() without return types