docs: def _idToStr(self, x):
          """
          Convert VCD id in int to string
          """
          if x < 0:
              sign = -1
          elif x == 0:
              return self._idChars[0]
          else:
              sign = 1
          x *= sign
          digits = []
          while x:
              digits.append(self._idChars[x % self._idCharsCnt])
              x //= self._idCharsCnt
          if sign < 0:
              digits.append('-')
          digits.reverse()
  
          return ''.join(digits)