Object layer visibility - Applescript

Hi!

This script can change links layers visibility:

https://sites.google.com/site/dtpscripting/indesign-scripts/linklayersvisibility-jsx

I worked a little bit on the script.. I could resolve the error but now I am wondering how I can put the visiblility of all graphic layers to true..

tell application "Adobe InDesign CS5.5"

  activate

          if active book exists then

          else

                    set GetParentPath to ((choose file with prompt "Kies een Indesignbook:" of type "IDb5.5"))

  open GetParentPath

  delay 1

          end if

end tell

tell application "Adobe InDesign CS5.5"

          tell active book

                    set fileList to full name of book contents

          end tell

  --general

          set CountryArray to {"BE", "FR", "NL", "EX", "DE", "NO"}

          set CountryID to choose from list CountryArray with prompt "Selecteer de juiste catalogus prijzen." OK button name "Update book" without multiple selections allowed

          if CountryID is false then return

          set Country to characters 1 thru 2 of item 1 of CountryID as string

  --make all layers visible

          repeat with aFile in fileList

                    set theDoc to open aFile

                    set myDocument to active document

                    tell myDocument

                              set layers's visible to true

                              set var_linkcount to count of links

                              repeat with j from 1 to var_linkcount

                                        tell graphic layer options of parent of link j

                                                  set ActiveLayerOption to (Country & " prices")

                                                  set DeactivateLayerOption to {}

                                                  repeat with x from 1 to count of CountryArray

                                                            set i to item x of CountryArray as string

                                                            if i is Country then

                                                                      set thisLayer to (i & " prices")

                                                                      try

                                                                                set current visibility of graphic layer thisLayer to true

                                                                      end try

                                                            else

                                                                      set thisLayer to (i & " prices")

                                                                      try

                                                                                set current visibility of graphic layer thisLayer to false

                                                                      end try

                                                            end if

                                                  end repeat

                                        end tell

                              end repeat

                    end tell

  close theDoc saving yes

          end repeat

          display dialog "Layers zijn aangepast"

end tell