new_contents: '''Test Span.as_doc() doesn't segfault'''
  from ...tokens import Doc 
  from ...vocab import Vocab
  from ... import load as load_spacy
  
  
  def test_issue1537():
      string = 'The sky is blue . The man is pink . The dog is purple .'
      doc = Doc(Vocab(), words=string.split())
      doc[0].sent_start = True
      for word in doc[1:]:
          if word.nbor(-1).text == '.':
              word.sent_start = True
          else:
              word.sent_start = False
  
      sents = list(doc.sents)
      sent0 = sents[0].as_doc()
      sent1 = sents[1].as_doc()
      assert isinstance(sent0, Doc)
      assert isinstance(sent1, Doc)
  
  
  # Currently segfaulting, due to l_edge and r_edge misalignment
  #def test_issue1537_model():
  #    nlp = load_spacy('en')
  #    doc = nlp(u'The sky is blue. The man is pink. The dog is purple.')
  #    sents = [s.as_doc() for s in doc.sents]
  #    print(list(sents[0].noun_chunks))
  #    print(list(sents[1].noun_chunks))
  
subject: Add test for Issue #1537