code: def is_valid_vietnam_word(word):
      chars = list(word)
      nguyen_am_index = -1
      for index, char in enumerate(chars):
          x, y = nguyen_am_to_ids.get(char, (-1, -1))
          if x != -1:
              if nguyen_am_index == -1:
                  nguyen_am_index = index
              else:
                  if index - nguyen_am_index != 1:
                      return False
                  nguyen_am_index = index
      return True
  
file_path: underthesea/examples/text_normalize/tools/nvh.py
imports: import regex
label_desc: Use image node_id 6 for calling a global function with example usage: is_valid_vietnam_word(word) and returns: True, False