code: def radial_distortion(camera, x):
      r_sq = np.square(x).sum(axis=-1, keepdims=True)
      return x * (1.0 + r_sq * (camera.k1 + camera.k2 * r_sq))
  
file_path: nerfies/third_party/pycolmap/pycolmap/camera.py
imports: import numpy
  from scipy.optimize import root
label_desc: Use image node_id 2 for calling a global function with example usage: radial_distortion(camera, x) and returns: unknown