apply code suggestions

Co-authored-by: John Paul E. Balandan, CPA <paulbalandan@gmail.com>

Author: michalsn

src/TaskLog.php

@@ -74,11 +74,11 @@ public function __get(string $key)
  /**
  * Unify output to string.
  *
- * @param array|bool|int|string|null $value
+ * @param array<int, string>|bool|int|string|null $value
  *
  * @return string|null
  */
- protected function setOutput($value)
+ private function setOutput($value): ?string
  {
  if (is_string($value) || $value === null) {
  return $value;