input: def count_unique_case_pairs(word: str) -> int:
      """
      You are given a string word. A letter is considered special if it is found in both its lowercase and uppercase forms in word.
  
      Return the count of such special letters in word.
  
      Examples:
      >>> word = "aaAbcBC"
      3
      >>> word = "abc"
      0
      >>> word = "abBCab"
      1
  
      Constraints:
      1 <= word.length <= 50
      word contains only lowercase and uppercase English letters.
      """
output:     
      unique_cases = set(word)
      count = 0
      
      for char in unique_cases:
          if char.islower() and char.upper() in unique_cases:
              count += 1
          elif char.isupper() and char.lower() in unique_cases:
              count += 1
              
      return count // 2  # Each pair is counted twice
  