docs: def fan_triangulate(indices):
      """Return an array of vertices in triangular order using a fan triangulation algorithm."""
      if len(indices[0]) != 4:
          raise ValueError("Assumes working with a sequence of quad indices")
      new_indices = []
      for face in indices:
          new_indices.extend([face[:-1], face[1:]])
      return np.array(new_indices)