code: def test_spans_string_fn(doc):
      span = doc[0:4]
      assert len(span) == 4
      assert span.text == "This is a sentence"
  
imports: import numpy
  import pytest
  from numpy.testing import assert_array_equal
  from thinc.api import get_current_ops
  from spacy.attrs import LENGTH, ORTH
  from spacy.lang.en import English
  from spacy.tokens import Doc, Span, Token
  from spacy.util import filter_spans
  from spacy.vocab import Vocab
  from ..util import add_vecs_to_vocab
  from .test_underscore import clean_underscore
label_desc: Use image node_id 15 for calling a global function with example usage: test_spans_string_fn(doc) without return types