code: public function decode($value, Field $field, Codec $codec = null)
      {
          $value = trim((string) $value);
          if ($value === '') {
              return null;
          }
  
          if (!$this->decodeFromBase64) {
              return $value;
          }
  
          $value = base64_decode($value, true);
  
          if (false === $value) {
              throw new DecodeValueFailed($value, $field, 'Strict base64_decode failed.');
          }
  
          return $value;
      }
docs: {@inheritdoc}