DatastoreInputReader filter item in list

[RubenMattan]

When you want to check if a list contains an item you normally check by doing .filter("list =", item) but DatastoreInputReader validation is expecting a list instead of an item.

Should be
mapper_params = { "filters": [("list", "=", item)] }
instead of
mapper_params = { "filters": [("list", "=", [item])] }

Validate in source code

[eko-wibowo]

@RubenMattan I opened a pull request for it #94 this seems only affect db.Model as ndb is fine.