code: def test_numpy_not_installed():
      summarizer = LexRankSummarizer()
  
      numpy = lex_rank_module.numpy
      lex_rank_module.numpy = None
  
      with pytest.raises(ValueError):
          summarizer(build_document(), 10)
  
      lex_rank_module.numpy = numpy
  
imports: from __future__ import absolute_import
  from __future__ import division, print_function, unicode_literals
  import math
  import numpy
  import pytest
  import sumy.summarizers.lex_rank
  from sumy.nlp.stemmers.czech import stem_word
  from sumy.nlp.tokenizers import Tokenizer
  from sumy.parsers.plaintext import PlaintextParser
  from sumy.summarizers.lex_rank import LexRankSummarizer
  from sumy.utils import get_stop_words
  from ..utils import build_document, load_resource
label_desc: Use image node_id 1 for calling a global function with example usage: test_numpy_not_installed() without return types