public function is_plugin_installed( $slug )
	{
		$element = $this->search_plugin( $slug );
		if ( count( $element ) ) {
			return true;
		} else {
			return false;
		}
	}
public function is_plugin_installed( $slug )
	{
		$element = $this->search_plugin( $slug );
		if ( count( $element ) ) {
			return true;
		} else {
			return false;
		}
	}
public function is_plugin_installed ( $ slug ) { $ element = $ this -> search_plugin ( $ slug ) ; if ( count ( $ element ) ) { return true ; } else { return false ; } }
Check the plugin is installed.

@param string $slug The slug of the plugin.
@return bool Return true if plugin is installed.
@throws \Exception
Check the plugin is installed .