code: function within($start, $finish): self {
      $target = $this->hasFlag('length') ? $this->getLength($this->target) : $this->target;
      return $this->expect($target, logicalAnd(greaterThanOrEqual($start), lessThanOrEqual($finish)));
    }
docs: Reports an error if the target is greater than or less than the specified bounds.
  @param int|float $start The lowerbound inclusive.
  @param int|float $finish The upperbound inclusive.
  @return self This instance.