def all_write!
      will_change!
      permissions.keys.each do |perm|
        permissions[perm].write! true
      end
    end
def all_write!
      will_change!
      permissions.keys.each do |perm|
        permissions[perm].write! true
      end
    end
Grants write permission on all existing users and roles attached to this object.
 @example
  object.acl
  #    { "*":          { "read" : true },
  #      "3KmCvT7Zsb": { "read" : true, "write": true },
  #      "role:Admins": { "write": true }
  #     }
  object.acl.all_write!
  # Outcome:
  #    { "*":          { "read" : true, "write": true },
  #      "3KmCvT7Zsb": { "read" : true, "write": true },
  #      "role:Admins": { "write": true }
  #     }
 @version 1.7.2
 @return [Array] list of ACL keys