code: def _visibleToRealColumn(self, text, visiblePos):
          
          if visiblePos == 0:
              return 0
          elif not '\t' in text:
              return visiblePos
          else:
              currentIndex = 1
              for currentVisiblePos in self._visibleCharPositionGenerator(text):
                  if currentVisiblePos >= visiblePos:
                      return currentIndex - 1
                  currentIndex += 1
  
              return None
docs: If \t is used, real position of symbol in block and visible position differs
          This function converts visible to real.
          Bigger value is returned, if visiblePos is in the middle of \t, None if text is too short