class_docstr: KnowledgeGraph link prediction dataset
  
  The dataset contains a graph depicting the connectivity of a knowledge
  base. Currently, the knowledge bases from the
  `RGCN paper <https://arxiv.org/pdf/1703.06103.pdf>`_ supported are
  FB15k-237, FB15k, wn18
  
  Parameters
  -----------
  name : str
      Name can be 'FB15k-237', 'FB15k' or 'wn18'.
  reverse : bool
      Whether add reverse edges. Default: True.
  raw_dir : str
      Raw file directory to download/contains the input data directory.
      Default: ~/.dgl/
  force_reload : bool
      Whether to reload the dataset. Default: False
  verbose : bool
      Whether to print out progress information. Default: True.
  transform : callable, optional
      A transform that takes in a :class:`~dgl.DGLGraph` object and returns
      a transformed version. The :class:`~dgl.DGLGraph` object will be
      transformed before every access.
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code: def __len__(self):
      return 1
  
imports: from __future__ import absolute_import
  import os, sys
  import pickle
  import networkx
  import numpy
  import scipy.sparse
  from ..None import backend
  from ..convert import graph
  from ..utils import retry_method_with_fix
  from .dgl_dataset import DGLBuiltinDataset
  from .utils import _get_dgl_url, deprecate_function, deprecate_property, download, extract_archive, generate_mask_tensor, get_download_dir, load_graphs, load_info, makedirs, save_graphs, save_info
label_desc: Use image node_id 8 for calling the KnowledgeGraphDataset obj's underlying member method code with example usage: obj.__len__() and returns: int