code: def isRotationMatrix(R):
      """checks if a matrix is a valid rotation matrix(whether orthogonal or not)"""
      Rt = np.transpose(R)
      shouldBeIdentity = np.dot(Rt, R)
      I = np.identity(3, dtype=R.dtype)
      n = np.linalg.norm(I - shouldBeIdentity)
      return n < 1e-6
  
file_path: insightface/python-package/insightface/thirdparty/face3d/mesh/transform.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  import math
  from math import cos, sin
label_desc: Use image node_id 13 for calling a global function with example usage: isRotationMatrix(R) and returns: unknown