validate method
Implementation
Map<String, dynamic> validate() {
// check for the id length
int idSize = utf8.encode(id).length;
if (idSize > DocRestrictions.maxIdLength) {
throw DbDocValidationException(
'${DBRKeys.id} max length is ${DocRestrictions.maxIdLength} bytes');
}
// checking for the _collections keyword
if (doc[DBRKeys.collections] != null) {
throw DbDocValidationException(
'you can\'t use ${DBRKeys.collections} keyword as it is reserved');
}
// update the id
doc[DBRKeys.id] = id;
// doc[DBRKeys.collections] = [];
return doc;
}