How do I reset a field

Frappe Framework Customization
1

I created a custom field in sales order called company_abbr that has options: company.abbr

two questions

  1. is company_abbr a point to company.abbr or just copies the value?
  2. I would like to reset company_abbr to be nil. I tried company_abbr = None but I get an error: AttributeError: can’t set attribute

can someone help? thanks in advance.

2

You have to change it in Company settings

3

I need to do this programmatically. I would like to keep the company settings.