class_docstr: Computes the rotation-invariant Point Pair Features
  (functional name: :obj:`point_pair_features`).
  
  .. math::
      \left( \| \mathbf{d_{j,i}} \|, \angle(\mathbf{n}_i, \mathbf{d_{j,i}}),
      \angle(\mathbf{n}_j, \mathbf{d_{j,i}}), \angle(\mathbf{n}_i,
      \mathbf{n}_j) \right)
  
  of linked nodes in its edge attributes, where :math:`\mathbf{d}_{j,i}`
  denotes the difference vector between, and :math:`\mathbf{n}_i` and
  :math:`\mathbf{n}_j` denote the surface normals of node :math:`i` and
  :math:`j` respectively.
  
  Args:
      cat (bool, optional): If set to :obj:`False`, all existing edge
          attributes will be replaced. (default: :obj:`True`)
code: def __init__(self, cat: bool = True):
      self.cat = cat
  
file_path: pytorch_geometric/torch_geometric/transforms/point_pair_features.py
imports: import torch
  import torch_geometric
  from torch_geometric.data import Data
  from torch_geometric.data.datapipes import functional_transform
  from torch_geometric.transforms import BaseTransform
label_desc: Use image node_id 1 to create a new PointPairFeatures object from inherited base classes: BaseTransform with example: obj = PointPairFeatures(cat)