public function singleton() {
		$key = sprintf( 'entry_type_id.post_type.%s', $this->get_post_type() );

		if ( papi()->exists( $key ) ) {
			return true;
		}

		papi()->singleton( $key, $this->get_id() );

		return false;
	}
public function singleton() {
		$key = sprintf( 'entry_type_id.post_type.%s', $this->get_post_type() );

		if ( papi()->exists( $key ) ) {
			return true;
		}

		papi()->singleton( $key, $this->get_id() );

		return false;
	}
public function singleton ( ) { $ key = sprintf ( 'entry_type_id.post_type.%s' , $ this -> get_post_type ( ) ) ; if ( papi ( ) -> exists ( $ key ) ) { return true ; } papi ( ) -> singleton ( $ key , $ this -> get_id ( ) ) ; return false ; }
Check if the entry type is a singleton.

@return bool
Check if the entry type is a singleton .