code: public function validate($value, Constraint $constraint): void
      {
          if (!$constraint instanceof UniqueEmail) {
              throw new UnexpectedTypeException($constraint, UniqueEmail::class);
          }
  
          if (null !== $value &&
              !is_scalar($value) &&
              !(\is_object($value) && method_exists($value, '__toString'))
          ) {
              throw new UnexpectedTypeException($value, 'string');
          }
  
          $value = (string) $value;
  
          if ('' === $value) {
              return;
          }
  
          if ($this->emailExists($constraint, $value)) {
              $this->context->buildViolation($constraint->message)
                  ->setCode(UniqueEmail::NOT_UNIQUE_ERROR)
                  ->setParameter('{{ value }}', $this->formatValue($value, self::OBJECT_TO_STRING | self::PRETTY_DATE))
                  ->addViolation();
          }
      }
docs: {@inheritdoc}