class_docstr: Test some basic splitters.
code: def test_specified_split(self):
      solubility_dataset = load_solubility_data()
      random_splitter = dc.splits.SpecifiedSplitter(
          valid_indices=[7], test_indices=[8]
      )
      train_data, valid_data, test_data = random_splitter.split(
          solubility_dataset
      )
      assert len(train_data) == 8
      assert len(valid_data) == 1
      assert len(test_data) == 1
  
imports: import os
  import unittest
  import numpy
  import deepchem
  from deepchem.data import NumpyDataset
  from deepchem.splits import IndexSplitter
label_desc: Use image node_id 23 for calling the TestSplitter obj's underlying member method code with example usage: obj.test_specified_split() without return types