input: Write a python function to calculate the similarity score of two strings based on common words.
  assert get_similarity_score("hello world", "hello") == 0.5
  assert get_similarity_score("the quick brown fox", "the quick brown dog") == 0.75
  assert get_similarity_score("python code", "python programming language") == 0.0
output: def get_similarity_score(str1, str2):
      words1 = set(str1.split())
      words2 = set(str2.split())
      common_words = words1 & words2
      total_words = words1 | words2
      if not total_words:
          return 0.0
      return len(common_words) / len(total_words)