docs: def save_obj(self, path, update_normals=True):
          """Save data with OBJ format
          :param stl path:
          :param bool update_normals:
          """
          if update_normals:
              self.update_normals()
  
          # Create triangle_list
          vectors_key_list = []
          vectors_list = []
          normals_key_list = []
          normals_list = []
          triangle_list = []
          for i, vector in enumerate(self.vectors):
              one_triangle = []
              for j in range(3):
                  v_key = ",".join(map(str, self.vectors[i][j][:3]))
                  if v_key in vectors_key_list:
                      v_index = vectors_key_list.index(v_key)
                  else:
                      v_index = len(vectors_key_list)
                      vectors_key_list.append(v_key)
                      vectors_list.append(self.vectors[i][j][:3])
                  one_triangle.append(v_index + 1)
  
              n_key = ",".join(map(str, self.normals[i][:3]))
              if n_key in normals_key_list:
                  n_index = normals_key_list.index(n_key)
              else:
                  n_index = len(normals_key_list)
                  normals_key_list.append(n_key)
                  normals_list.append(self.normals[i][:3])
  
              # print(normals_list)
              triangle_list.append((one_triangle, n_index + 1))
  
          with open(path, "wb") as fh:
              print("# {} {}".format(__title__, __version__), file=fh)
              print("# {}".format(datetime.datetime.now()), file=fh)
              print("# {}".format(__url__), file=fh)
              print("", file=fh)
              for v in vectors_list:
                  print("v {} {} {}".format(v[0], v[1], v[2]), file=fh)
              for vn in normals_list:
                  print("vn {} {} {}".format(vn[0], vn[1], vn[2]), file=fh)
              for t in triangle_list:
                  faces = t[0]
                  normal = t[1]
  
                  print("f {}//{} {}//{} {}//{}".format(
                      faces[0], normal,
                      faces[1], normal,
                      faces[2], normal,
                  ), file=fh)