class ActiveAdmin::CSVBuilder

def self.default_for_resource(resource)

resource's content columns
The CSVBuilder's columns would be Id followed by this
Return a default CSVBuilder for a resource 
def self.default_for_resource(resource)
  new.tap do |csv_builder|
    csv_builder.column(:id)
    resource.content_columns.each do |content_column|
      csv_builder.column(content_column.name.to_sym)
    end
  end
end