cache option does not work with Reconstructor

[weaversam8]

Describe the bug

If an lalr grammar is loaded from a cached file, and then the parser is passed to initialize a Reconstructor(...) class, initialization fails with the following error:

AttributeError: 'Lark' object has no attribute 'grammar'

To Reproduce

1. Open a parser with Lark.open(...) while setting the cache argument to a file path.
2. Try to initialize a Reconstructor(...) with that parser.