Add enum for handling check_instances

[sebastian-goeldi]

Allows different handling if any instance in the @cell decorated cell is off-grid or a non-90° rotation:

• CHECK_INSTANCES.ERROR ("error"): Throw an error (default)
• CHECK_INSTANCES.FLATTEN ("flatten"): Flatten the cell
• CHECK_INSTANCES.VINSTANCES ("vinstances"): Convert any offending instance to a VInstance
• CHECK_INSTANCES.NONE (none): Do nothing and continue

Example usage:

test.py

```python import kfactory as kf @kf.kcl.cell def rotated_bend() -> kf.KCell: c = kf.KCell() bend = c << kf.cells.euler.bend_euler(width=1, radius=10, layer=kf.kcl.layer(1, 0)) bend.drotate(30) straight = c << kf.cells.straight.straight( width=1, length=10, layer=kf.kcl.layer(2, 0) ) straight.connect("o1", bend, "o2") return c rotated_bend().show() ```

Run:

KFACTORY_CHECK_INSTANCES='vinstances' KFACTORY_LOGFILTER_LEVEL="DEBUG" KFACTORY_ALLOW_LAYER_MISMATCH=on python test.py

Or for single usage:

@cell(check_instances=config.CHECK_INSTANCES.VINSTANCES)

@tvt173

[tvt173]

trying to understand how to set the behavior globally... the KFACTORY_CHECK_INSTANCES etc. that you mention above, those are meant to be environment variables? or how should they be set to change global behavior when executing a script?

[tvt173]

for example, i would have expected that setting this in my script would have configured the setting globally, but i still see the same error

kf.config.check_instances = kf.conf.CHECK_INSTANCES.VINSTANCES