use std::convert::TryFrom;
use std::ops::Deref;
use std::time;
use crate::{
HashAlgorithm,
Result,
SignatureType,
};
use crate::types::{
ReasonForRevocation,
};
use crate::crypto::Signer;
use crate::packet::{
Key,
key,
signature,
Signature,
UserAttribute,
UserID,
};
use crate::cert::prelude::*;
/// A builder for revocation certificates for OpenPGP certificates.
///
/// A revocation certificate for an OpenPGP certificate (as opposed
/// to, say, a subkey) has two degrees of freedom: the certificate,
/// and the key used to sign the revocation certificate.
///
/// Normally, the key used to sign the revocation certificate is the
/// certificate's primary key. However, this is not required. For
/// instance, if Alice has marked Robert's certificate (`R`) as a
/// [designated revoker] for her certificate (`A`), then `R` can
/// revoke `A` or parts of `A`. In this case, the certificate is `A`,
/// and the key used to sign the revocation certificate comes from
/// `R`.
///
/// [designated revoker]: https://tools.ietf.org/html/rfc4880#section-5.2.3.15
///
/// # Examples
///
/// Revoke `cert`, which was compromised yesterday:
///
/// ```rust
/// use sequoia_openpgp as openpgp;
/// # use openpgp::Result;
/// use openpgp::cert::prelude::*;
/// use openpgp::policy::StandardPolicy;
/// use openpgp::types::ReasonForRevocation;
/// use openpgp::types::RevocationStatus;
/// use openpgp::types::SignatureType;