diff --git a/include/wb/Snaks.php b/include/wb/Snaks.php
index cfef4dd..58264dd 100644
--- a/include/wb/Snaks.php
+++ b/include/wb/Snaks.php
@@ -1,131 +1,131 @@
 <?php
 # Boz-MW - Another MediaWiki API handler in PHP
-# Copyright (C) 2017, 2018, 2019 Valerio Bozzolan
+# Copyright (C) 2017-2023 Valerio Bozzolan, contributors
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License as published by
 # the Free Software Foundation, either version 3 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU Affero General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 # Wikibase
 namespace wb;
 
 /**
  * A Snak collector
  *
  * @since 2019-07-18
  */
 class Snaks {
 
 	/**
 	 * All the Snaks indexed by property
 	 */
 	private $snaks = [];
 
 	/**
 	 * Constructor
 	 *
 	 * @param array $snaks Initial set of snaks
 	 */
 	public function __construct( $snaks = [] ) {
 		foreach( $snaks as $snak ) {
 			$this->add( $snak );
 		}
 	}
 
 	/**
 	 * Add a Snak
 	 *
 	 * @param object $snak
 	 * @return this
 	 */
 	public function add( Snak $snak ) {
 
 		// eventually init the property container of snaks
 		$property = $snak->getProperty();
 		if( !isset( $this->snaks[ $property ] ) ) {
 			$this->snaks[ $property ] = [];
 		}
 
 		// append
 		$this->snaks[ $property ][] = $snak;
 
 		return $this;
 	}
 
 	/**
 	 * Get all the snaks from a certain property
 	 *
 	 * @param string $property Property name e.g. 'P123'
 	 * @return array
 	 */
 	public function getInProperty( $property ) {
 		if( $this->hasInProperty( $property ) ) {
 			return $this->snaks[ $property ];
 		}
 		return [];
 	}
 
 	/**
 	 * Check if there are some snaks in this property
 	 */
 	public function hasInProperty( $property ) {
 		return !empty( $this->snaks[ $property ] );
 	}
 
 	/**
 	 * Check if there are not snaks
 	 *
 	 * @return boolean
 	 */
 	public function isEmpty() {
-		return !empty( $this->snaks );
+		return empty( $this->snaks );
 	}
 
 	/**
 	 * Get all the snaks indexed by property
 	 *
 	 * @return array
 	 */
 	public function getAllByProperty() {
 		return $this->snaks;
 	}
 
 	/**
 	 * Count all the snaks
 	 *
 	 * @return int
 	 */
 	public function count() {
 		$n = 0;
 		foreach( $this->getAll() as $property => $snaks ) {
 			$n += count( $snaks );
 		}
 		return $n;
 	}
 
 	/**
 	 * Convert this object to an associative array suitable for JSON encoding
 	 *
 	 * @return array
 	 */
 	public function toData() {
 		$data = [];
 		foreach( $this->getAllByProperty() as $property => $snaks ) {
 			$data[ $property ] = [];
 			foreach( $snaks as $snak ) {
 				$data[ $property ][] = $snak->toData();
 			}
 		}
 		return $data;
 	}
 
 }