# File lib/simp/cli/config/items/set_server_hieradata_action_item.rb, line 44
    def add_yaml_entry(hiera_key)
      hiera_item = @config_items.fetch( hiera_key )
      full_yaml_string = hiera_item.to_yaml_s
      if full_yaml_string.nil?
        raise InternalError.new("YAML string for #{hiera_key} is not set")
      end

      debug( "Adding #{hiera_key} to #{File.basename(@file)}" )
      yaml = IO.readlines(@file)
      line_written = false
      File.open(@file, "w") do |f|
        yaml.each do |line|
          line.chomp!
          if line =~ /^classes\s*:/
            f.puts full_yaml_string
            f.puts line
            line_written = true
          else
            f.puts line
          end
        end

        unless line_written
          f.puts full_yaml_string
        end
      end
    end