How can we filter by using child tables

[anaspa]

Hi
How can we change the below one as

User.find()
.populate('pets')
.exec(function(err, users) {
if(err) // handle error

// The users object would look something like the following
// [{
// id: 123,
// firstName: 'Foo',
// lastName: 'Bar',
// pets: [{
// id: 1,
// breed: 'labrador',
// type: 'dog',
// name: 'fido',
// user: 123
// }]
// }]
});

to find all users who has pet type is dog