Name: wp-hide/ob_start_callback
Type: Filter
Arguments: $buffer

This is the filter through which the plugin allow changes to outputted HTML buffer.

        add_filter( 'wp-hide/ob_start_callback', 'custom_ob_start_callback' ); 
        function custom_ob_start_callback( $buffer )
            {
                
                $buffer =   str_replace("Powered by WordPress" , "", $buffer);
                
                return $buffer;
                   
            }

The $buffer contain the full HTML data which is being sent to browser as server response.