includes/class-freemius.php
function init_sandbox( $secret_key ) {
            $this->_plugin->secret_key = $secret_key;

            // Update plugin details.
            FS_Plugin_Manager::instance( $this->_module_id )->update( $this->_plugin, true );
        }
function init_sandbox( $secret_key ) {
            $this->_plugin->secret_key = $secret_key;

            // Update plugin details.
            FS_Plugin_Manager::instance( $this->_module_id )->update( $this->_plugin, true );
        }
function init_sandbox ( $ secret_key ) { $ this -> _plugin -> secret_key = $ secret_key ; // Update plugin details.
 FS_Plugin_Manager :: instance ( $ this -> _module_id ) -> update ( $ this -> _plugin , true ) ; }
Set Freemius into sandbox mode for debugging.

@author Vova Feldman (@svovaf)
@since  1.0.4

@param string $secret_key
Set Freemius into sandbox mode for debugging .