How to add readonly inline on django admin

After a while of trying to find the name I figured out thanks to this answer, so I checked the names at self.opts.local_fields and found the name of the middle table and added it to readonly_fields, setting can_delete to False.

class SummaryInline(admin.TabularInline):
    model = ParserError.summaries.through
    readonly_fields = ('myclasssummary',)
    can_delete = False

pretty simple but took me a while so I figured out it was a good idea to add it here.