code: def test_read_from_file_ag_news_corpus_and_truncates_properly(self):
      reader = TextClassificationJsonReader(max_sequence_length=5)
      ag_path = (
          AllenNlpTestCase.FIXTURES_ROOT
          / "data"
          / "text_classification_json"
          / "ag_news_corpus.jsonl"
      )
      instances = list(reader.read(ag_path))
  
      instance1 = {
          "tokens": ["Memphis", "Rout", "Still", "Stings", "for"],
          "label": "2",
      }
      instance2 = {
          "tokens": ["AP", "-", "Eli", "Manning", "has"],
          "label": "2",
      }
      instance3 = {
          "tokens": ["A", "conference", "dedicated", "to", "online"],
          "label": "4",
      }
  
      assert len(instances) == 3
      fields = instances[0].fields
      assert [t.text for t in fields["tokens"].tokens] == instance1[
          "tokens"
      ]
      assert fields["label"].label == instance1["label"]
      fields = instances[1].fields
      assert [t.text for t in fields["tokens"].tokens] == instance2[
          "tokens"
      ]
      assert fields["label"].label == instance2["label"]
      fields = instances[2].fields
      assert [t.text for t in fields["tokens"].tokens] == instance3[
          "tokens"
      ]
      assert fields["label"].label == instance3["label"]
  
file_path: allennlp/tests/data/dataset_readers/text_classification_json_test.py
imports: import pytest
  from typing import List
  import spacy
  from allennlp.data.dataset_readers import TextClassificationJsonReader
  from allennlp.common.testing import AllenNlpTestCase
  from allennlp.data.tokenizers.sentence_splitter import SpacySentenceSplitter
  from allennlp.common.util import get_spacy_model
label_desc: Use image node_id 3 for calling the TestTextClassificationJsonReader obj's underlying member method code with example usage: obj.test_read_from_file_ag_news_corpus_and_truncates_properly() without return types