code: protected function pointer(string $path, ?string $member = null): array
      {
          /** Member can be '0' which is an empty string. */
          $withoutMember = is_null($member) || '' === $member;
          $pointer = !$withoutMember ? sprintf('%s/%s', rtrim($path, '/'), $member) : $path;
  
          return [Error::SOURCE_POINTER => $pointer];
      }
docs: Create a source pointer for the specified path and optional member at that path.
  
  @param string $path
  @param string|null $member
  @return array