–– Pkl Error ––
Cannot extend non-open module `extendModule1`.

x | extends "extendModule1.pkl"
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
at invalidExtend2 (file:///$snippetsDir/input/modules/invalidExtend2.pkl)

By default, modules are closed for extension.
To make a module extensible, add an `open` modifier: `open module my_module; ...`
