public function is_valid_lookup() {
		if ( strpos( strtolower( $this->lookup_class ), strtolower( $this->namespace ) ) !== false ) {
			if ( false !== $this->option( 'exclude' ) ) {
				foreach ( $this->option( 'exclude' ) as $namespace ) {
					if ( strpos( strtolower( $this->lookup_class ), strtolower( $namespace ) ) !== false ) {
						return false;
					}
				}
			}
			return true;
		}
		return false;
	}