before_batch_import and after_batch_import options

 ActiveAdmin.register Post  do
        active_admin_import validate: true,
        before_batch_import: proc { |import|
           import.file #current file used
           import.resource #ActiveRecord class to import to
           import.options # options
           import.result # result before bulk iteration
           import.headers # CSV headers
           import.csv_lines #lines to import
           import.model #template_object instance
        },
        after_batch_import: proc{ |import|
           #the same
        }
    end