Flatten does not flatten empty objects or arrays

Issue:

Suppose I have the following object

`{
"foo": {
"bar": "hello-world"
},
"data": {},
"tests": []
}`

I would expect this object to be flattened if I need it for some sort of operation which does not support complex objects.
Perhaps it would be flattened in this way
`{
"foo.bar": "hello-world",
"data": "{}",
"tests": "[]"
}`

Or, perhaps there is a better way to do this; but, what actually occurs is the following

`{
"foo.bar": "hello-world",
"data": {},
"tests": []
}`

Where, in reality, this has not been flattened. There still exists nested objects, they are just empty.