var validTasks = Tasks.all({invalid: false}, function(err, tasks) {
    // Do something
});

var SaveInvalid = require('modella-save-invalid');
SaveInvalid.invalidAttr = 'invalid' // Optional, will persist the status into the database
SaveInvalid.completeAttr = 'complete' // Optional, will persist the status into the database, inverse of invalid.
User.use(SaveInvalid); // Assume some model w/ validations.
var user = new User();
user.username('Bobby');
// Assume user is still invalid.
user.save() // Will emit error and not save.
user.save(function(err) {
  err == undefined // Will be false
});
user.save(true) // Will save user in db and user.invalid() will be true
user.save(true, function(err) {
  err == undefined // Will be true (assuming no sync-layer errors)
});