code: def random_unit(size=3):
      
      while True:
          result = np.random.normal(0, 1, size)
          length = np.linalg.norm(result)
          if length > 1e-3:
              return result/length
docs: Return a random unit vector of the given dimension
  
         Optional argument:
           size  --  the number of dimensions of the unit vector [default=3]