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_true_type.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
    
      def perform_validation
        std_font = FontType1::StandardFonts.standard_font?(self[:BaseFont])
        super(ignore_missing_font_fields: std_font)

        if self[:FontDescriptor].nil? && !std_font
          yield("Required field FontDescriptor is not set", false)
        end