class HexaPDF::Type::AcroForm::SignatureField::SeedValueDictionary

See: PDF2.0 s12.7.5.5
digest_method, lock_document and appearance_filter.
The available flags are: filter, sub_filter, v, reasons, legal_attestation, add_rev_info,
is optional.
If a flag is set it means that the associated entry is a required constraint. Otherwise it
== Flags
that is applied to the associated signature field.
A seed value dictionary contains information that constrains the properties of a signature