Consume chars until min/max is satisfied is valid.

def consume(self, chars, min=0, max=-1):
        """
        Consume chars until min/max is satisfied is valid.
        """
        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)