code: def vectors2angle(v1, v2):
      
      cosang = np.dot(v1, v2)
      sinang = np.linalg.norm(np.cross(v1, v2))
      return np.arctan2(sinang, cosang)
docs: Returns the angle in radians between vectors 'v1' and 'v2'.
  
      :param v1:
          vector, a numpy array
      :param v2:
          vector, a numpy array
      :returns:
          the angle in radians between the two vetors