reason property Leave feedback

The substitution message exactly as reported by the conversion pipeline, verbatim and unparsed.

For documents that expose font names structurally this may be None (use FontSubstitutionContext.original_font_name / FontSubstitutionContext.substitute_font_name); for others it carries the full human-readable description, which names both the missing and the substitute font.

@property
def reason(self):
    ...

• class FontSubstitutionContext