JavaScript Object.keys returning empty array

I'm trying to get the keys from a JavaScript Object. When I inspect the object I can see that there is a key value pair on the object but when I run Object.keys(myObject) I get an empty array returned. What am I doing wrong?

I'm following this documentation here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys

And the function which creates the object is as follows:

query: function () {
  var query = {}
  _.each(this.$el.find('input:checked'), function (el, index) {
    Object.defineProperty(query, el.id, {value: el.value})
  })
  return query
}