code: def _add_rician(sig, noise1, noise2):
      """
      Helper function to add_noise.
  
      This does the same as abs(sig + complex(noise1, noise2))
  
      """
      return np.sqrt((sig + noise1) ** 2 + noise2**2)
  
imports: import numpy
  from numpy import dot
  from dipy.core.geometry import sphere2cart
  from dipy.core.geometry import vec2vec_rotmat
  from dipy.core.gradients import GradientTable
  from dipy.reconst.utils import dki_design_matrix
  from scipy.special import jn
label_desc: Use image node_id 3 for calling a global function with example usage: _add_rician(sig, noise1, noise2) and returns: np