def generate_available_uuid_list(count = 100)
      new_uuids = (0..count).map { SecureRandom.hex(12).upcase }
      uniques = (new_uuids - (@generated_uuids + uuids))
      @generated_uuids += uniques
      @available_uuids += uniques
    end
def generate_available_uuid_list(count = 100)
      new_uuids = (0..count).map { SecureRandom.hex(12).upcase }
      uniques = (new_uuids - (@generated_uuids + uuids))
      @generated_uuids += uniques
      @available_uuids += uniques
    end
Pre-generates the given number of UUIDs. Useful for optimizing
 performance when the rough number of objects that will be created is
 known in advance.

 @param  [Integer] count
         the number of UUIDs that should be generated.

 @note   This method might generated a minor number of uniques UUIDs than
         the given count, because some might be duplicated a thus will be
         discarded.

 @return [void]