code: def multi_fcn(self, B, x):
      if (x < 0.0).any():
          raise OdrStop
      theta = pi * B[3] / 2.0
      ctheta = np.cos(theta)
      stheta = np.sin(theta)
      omega = np.power(2.0 * pi * x * np.exp(-B[2]), B[3])
      phi = np.arctan2((omega * stheta), (1.0 + omega * ctheta))
      r = (B[0] - B[1]) * np.power(
          np.sqrt(
              np.power(1.0 + omega * ctheta, 2)
              + np.power(omega * stheta, 2)
          ),
          -B[4],
      )
      ret = np.vstack(
          [B[1] + r * np.cos(B[4] * phi), r * np.sin(B[4] * phi)]
      )
      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, assert_allclose
  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 10 for calling the TestODR obj's underlying member method code with example usage: obj.multi_fcn(B, x) and returns: ret