`PlutoDependencyExplorer` not understanding importing local modules

Here's an MWE:
```julia
using PlutoDependencyExplorer
const PDE = PlutoDependencyExplorer;
struct SimpleCell <: PDE.AbstractCell
code
end
```
```julia
julia> let notebook = SimpleCell.(["mod = expr", "using .mod"])
empty_topology = PDE.NotebookTopology{SimpleCell}();
topology = PDE.updated_topology(
empty_topology,
notebook, notebook;
get_code_str = c -> c.code,
get_code_expr = c -> Meta.parse(c.code))
order = PDE.topological_order(topology);
order.runnable
end
SimpleCell[]
```
Ideally this should return
```julia
2-element Vector{SimpleCell}:
SimpleCell("mod = expr")
SimpleCell("using .mod")
```
This is manifesting in errors in Pluto when I try to import a locally defined module.