code: def test_init_with_fields_config(self):
      fields_config = {"a": int}
      model_selection = ModelSelection(fields_config=fields_config)
      self.assertEqual(2, len(model_selection._fields_config))
  
imports: import unittest
  from small_text.training.metrics import Metric
  from small_text.training.model_selection import ModelSelectionResult, ModelSelection, NoopModelSelection
label_desc: Use image node_id 6 for calling the ModelSelectionTest obj's underlying member method code with example usage: obj.test_init_with_fields_config() without return types