Converter

convert	description
empty	convert val to empty
nil	convert val to nil
big_text	convert val to big_text("text" * 50)
br_text	convert val to br_text("text\n" * 5)

For example, following configfile register seed data while replacing with nil

Default:
  Pref: 
    loop: 3
    col:
      name: ["Hokkaido", "Aomori", "Iwate"]
    convert:
      name: ["nil(0..2)"]

Result

Pref.pluck(:name) => [nil, nil, nil]

a little complex version

Default:
  Pref: 
    loop: 3
    col:
      name: ["Hokkaido", "Aomori", "Iwate"]
    convert:
      name: ["empty(0..0)", "nil(1..2)"]

Result

Pref.pluck(:name) => ["", nil, nil]