The "parent_edit_pre" filter is part of a group of dynamic filters. This filter runs in wp-admin when loading a post for editing.
When the 'parent_edit_pre' filter is called, it is passed two parameters: the parent post id and the id of the post to be edited
function filter_function_name( $parent_post_id, $post_id ) {
// Do post manipulation here
return $parent_post_id;
}
add_filter( 'parent_edit_pre', 'filter_function_name', 10, 2 );
Where 'filter_function_name' is the function WordPress should call when filter is run. Note that the filter function must return an integer after it is finished processing or the author will be empty.
filter_function_name should be unique function name. It cannot match any other function name already declared.