class ActiveAdmin::HasManyBuilder

def initialize(has_many_form, assoc, options)
  super has_many_form
  @assoc = assoc
  @options = extract_custom_settings!(options.dup)
  @options.reverse_merge!(for: assoc)
  @options[:class] = [options[:class], "inputs has_many_fields"].compact.join(' ')
  if sortable_column
    @options[:for] = [assoc, sorted_children(sortable_column)]
  end
end