src/core/validator/Validator.php
public static function isIndexSet(array& $data, string $key): bool
    {
        try {
            self::getArrayItemByPointSeparatedKey($data, $key);
            return true;
        } catch (Exception $e) {
            return false;
        }
    }
public static function isIndexSet(array& $data, string $key): bool
    {
        try {
            self::getArrayItemByPointSeparatedKey($data, $key);
            return true;
        } catch (Exception $e) {
            return false;
        }
    }
The method checks if the input tree contains an element with the specified
index (the index contains a point-separator of tiers)
@param mixed[] $data Input tree.
@param string $key The field name. The name of the nested field is formed by
the path of the tree the tiers of which are separated by the point.
@return boolean