class_docstr: ICEWS18 dataset for temporal graph
  
  Integrated Crisis Early Warning System (ICEWS18)
  
  Event data consists of coded interactions between socio-political
  actors (i.e., cooperative or hostile actions between individuals,
  groups, sectors and nation states). This Dataset consists of events
  from 1/1/2018 to 10/31/2018 (24 hours time granularity).
  
  Reference:
  
      - `Recurrent Event Network for Reasoning over Temporal Knowledge Graphs <https://arxiv.org/abs/1904.05530>`_
      - `ICEWS Coded Event Data <https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/28075>`_
  
  Statistics：
  
  - Train examples: 240
  - Valid examples: 30
  - Test examples: 34
  - Nodes per graph: 23033
  
  Parameters
  ----------
  mode: str
      Load train/valid/test data. Has to be one of ['train', 'valid', 'test']
  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.
  
  Attributes
  -------
  is_temporal : bool
      Is the dataset contains temporal graphs
  
  Examples
  --------
  >>> # get train, valid, test set
  >>> train_data = ICEWS18Dataset()
  >>> valid_data = ICEWS18Dataset(mode='valid')
  >>> test_data = ICEWS18Dataset(mode='test')
  >>>
  >>> train_size = len(train_data)
  >>> for g in train_data:
  ....    e_feat = g.edata['rel_type']
  ....    # your code here
  ....
  >>>
code: def save(self):
      graph_path = os.path.join(
          self.save_path, "{}_dgl_graph.bin".format(self.mode)
      )
      save_graphs(graph_path, self._graphs)
  
file_path: dgl/python/dgl/data/icews18.py
imports: import os
  import numpy
  from ..None import backend
  from ..convert import graph
  from .dgl_dataset import DGLBuiltinDataset
  from .utils import _get_dgl_url, load_graphs, loadtxt, save_graphs
label_desc: Use image node_id 4 for calling the ICEWS18Dataset obj's underlying member method code with example usage: obj.save() without return types