Private #validations
#validations: Partial<{ [ P in string | number | symbol]: FieldValidation<T, T> | Partial<{ [P in keyof T[P]]: FieldValidation<T[P], T[P]> | Partial<{ [P in keyof T[P][P]]: FieldValidation<T[P][P], T[P][P]> | Partial<{ [P in keyof T[P][P][P]]: FieldValidation<...> | Partial<...>; }>; }>; }> }>