docs: def getOccurrenceOfCharAtIndex(self, sym, index):
          '''
          This functions gets the FM-index value of a character at the specified position
          @param sym - the character to find the occurrence level
          @param index - the index we want to find the occurrence level at
          @return - the number of occurrences of char before the specified index
          '''
          #sampling method
          #get the bin we occupy
          binID = index >> self.bitPower
          
          #these two methods seem to have the same approximate run time
          if (binID << self.bitPower) == index:
              ret = self.partialFM[binID][sym]
          else:
              ret = self.partialFM[binID][sym] + np.bincount(self.bwt[binID << self.bitPower:index], minlength=6)[sym]
          return int(ret)