Correct method to fluent interface.

src/Datasource/EntityTrait.php

@@ -582,7 +582,7 @@ public function extractOriginalChanged(array $properties)
      * @param null|bool $isDirty true means the property was changed, false means
      * it was not changed and null will make the function return current state
      * for that property
-     * @return bool whether the property was changed or not
+     * @return bool Whether the property was changed or not
      */
     public function dirty($property = null, $isDirty = null)
     {
@@ -844,14 +844,16 @@ public function accessible($property, $set = null)
      * this entity came from if it is known.
      *
      * @param string $alias the alias of the repository
-     * @return string
+     * @return string|$this
      */
     public function source($alias = null)
     {
         if ($alias === null) {
             return $this->_registryAlias;
         }
         $this->_registryAlias = $alias;
+
+        return $this;
     }
 
     /**