How to get hierarchy showing via indents

[dbatten5]

I have the following class:

class Foo:
    def bar(self) -> str:
        x = "hello"
        return x

On running Trouble symbols toggle I see the following

I would expect to see the symbol for bar is nested under Foo but they are on the same indent line.

I saw the discussion here which recommends running Trouble lsp_document_symbols toggle but this doesn't fix my issue:

Is there a config option I'm missing? Or maybe an issue with my theme? Thanks