input: def num_common_substrings(s1: str, s2: str) -> int:
      """ Count the number of common substrings between two given strings.
      >>> num_common_substrings("abcd", "bae")
      1
      """
output:     count = 0
      set1 = set()
      set2 = set()
  
      for i in range(len(s1)):
          for j in range(i + 1, len(s1) + 1):
              set1.add(s1[i:j])
  
      for i in range(len(s2)):
          for j in range(i + 1, len(s2) + 1):
              set2.add(s2[i:j])
  
      common_substrings = set1 & set2
      count = len(common_substrings)
  
      return count