code: def consume(self, chars, min=0, max=-1):
          
          while self.current in chars and max != 0:
              min -= 1
              max -= 1
              if not self.inc():
                  break
  
          # failed to consume minimum number of characters
          if min > 0:
              self.parse_error(UnexpectedCharError)
docs: Consume chars until min/max is satisfied is valid.