You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: font_type3.rb
    path of file: ./repos/hexapdf/lib/hexapdf/type
    
    the code of the file until where you have to start completion: # -*- encoding: utf-8; frozen_string_literal: true -*-
#
#--
# This file is part of HexaPDF.
#

    
      def bounding_box
        matrix = self[:FontMatrix]
        bbox = self[:FontBBox].value
        if matrix[3] < 0 # Some writers invert the y-axis
          bbox = bbox.dup
          bbox[1], bbox[3] = -bbox[3], -bbox[1]
        end