code: def runge(self, x):
      return 1.0 / (1.0 + 25.0 * float(x * x))
  
file_path: essentia/test/src/unittests/standard/test_cubicspline.py
imports: from essentia_test import *
  from essentia.standard import *
  from numpy import r_, sin, pi
label_desc: Use image node_id 2 for calling the TestCubicSpline obj's underlying member method code with example usage: obj.runge(x) and returns: unknown