equals() public method

It matches if the $operand equals the value of the property named $propertyName. If $operand is NULL a strict check for NULL is done. For strings the comparison can be done with or without case-sensitivity.
public equals ( string $propertyName, mixed $operand, boolean $caseSensitive = true ) : object
$propertyName string The name of the property to compare against
$operand mixed The value to compare with
$caseSensitive boolean Whether the equality test should be done case-sensitive for strings
return object
 /**
  * @param QueryInterface $query
  * @param $nodeTypeFilter
  * @return array
  */
 protected function getNodeTypeFilterConstraints(QueryInterface $query, $nodeTypeFilter)
 {
     $includeNodeTypeConstraints = [];
     $excludeNodeTypeConstraints = [];
     $nodeTypeFilterParts = Arrays::trimExplode(',', $nodeTypeFilter);
     foreach ($nodeTypeFilterParts as $nodeTypeFilterPart) {
         $nodeTypeFilterPart = trim($nodeTypeFilterPart);
         if (strpos($nodeTypeFilterPart, '!') === 0) {
             $negate = true;
             $nodeTypeFilterPart = substr($nodeTypeFilterPart, 1);
         } else {
             $negate = false;
         }
         $nodeTypeFilterPartSubTypes = array_merge([$nodeTypeFilterPart], $this->nodeTypeManager->getSubNodeTypes($nodeTypeFilterPart, false));
         foreach ($nodeTypeFilterPartSubTypes as $nodeTypeFilterPartSubType) {
             if ($negate === true) {
                 $excludeNodeTypeConstraints[] = $query->logicalNot($query->equals('nodeType', $nodeTypeFilterPartSubType));
             } else {
                 $includeNodeTypeConstraints[] = $query->equals('nodeType', $nodeTypeFilterPartSubType);
             }
         }
     }
     $constraints = $excludeNodeTypeConstraints;
     if (count($includeNodeTypeConstraints) > 0) {
         $constraints[] = $query->logicalOr($includeNodeTypeConstraints);
     }
     return $constraints;
 }