src/Type/Definition/FieldDefinition.php
public function getArg($name)
    {
        foreach ($this->args ?: [] as $arg) {
            /** @var FieldArgument $arg */
            if ($arg->name === $name) {
                return $arg;
            }
        }

        return null;
    }
public function getArg($name)
    {
        foreach ($this->args ?: [] as $arg) {
            /** @var FieldArgument $arg */
            if ($arg->name === $name) {
                return $arg;
            }
        }

        return null;
    }
@param string $name

@return FieldArgument|null