code: def train_test_split(self, data, train_portion):
      time_len = data.shape[0]
      train_size = int(time_len * train_portion)
      train_data = np.array(data[:train_size])
      test_data = np.array(data[train_size:])
      return train_data, test_data
  
imports: from .dataset_loader import DatasetLoader
  from ..core.graph import StellarGraph, StellarDiGraph
  import itertools
  import logging
  import os
  import pandas
  import numpy
  from sklearn import preprocessing
  from ..core.experimental import experimental
label_desc: Use image node_id 2 for calling the METR_LA obj's underlying member method code with example usage: obj.train_test_split(data, train_portion) and returns: train_data,  test_data