Remove stylesheet.
Remove Python style 'import' as it is not used in Powershell.
Replace Python 'raise' with Powershell 'throw' keyword.
Remove Python 'pass' from Powershell keywords.
Remove 'yield' keyword as it is not used in Powershell.
Remove 'default' keyword as it is not used in Powershell.
Remove 'with' keyword as it is not used in Powershell.
Add 'do' and 'until' keywords to grammar.
Remove '(global)' which is not used in Powershell.
Add tests for 'if-elseif-else' keywords.