code: def explicit_fcn(self, B, x):
      ret = B[0] + B[1] * np.power(np.exp(B[2] * x) - 1.0, 2)
      return ret
  
imports: import tempfile
  import shutil
  import os
  import numpy
  from numpy import pi
  from numpy.testing import assert_array_almost_equal, assert_equal, assert_warns
  import pytest
  from pytest import raises
  from scipy.odr import Data, Model, ODR, RealData, OdrStop, OdrWarning, multilinear, exponential, unilinear, quadratic, polynomial
label_desc: Use image node_id 4 for calling the TestODR obj's underlying member method code with example usage: obj.explicit_fcn(B, x) and returns: ret