fn retain<F>(&mut self, _filter: F, _scope: Scope)
    where
        F: Fn(&KeyId, &CspSecretKey) -> bool,
    {
        unimplemented!()
    }
/// Keeps only entries in a scope for which the filter function returns
/// `true` and removes the rest.
///
/// Conversely, this removes entries in a given scope for which the filter
/// function returns `false`.
///
/// # Logs
/// Implementations SHOULD log the KeyId of any deleted keys
///
/// # Panics
/// This MAY panic if the predicate panics.
///
/// Details: Unlike e.g. `HashMap::filter_drain(..)` this does not
/// (handle the case where the filter panics)[https://doc.rust-lang.org/std/collections/struct.HashMap.html#method.drain_filter].
/// If the filter panics, the panic is likely to cause the secret key store
/// to crash. Thus lambdas MUST NEVER be taken from untrusted sources.
/// If panics are to be handled the predicate can be run in a separate
/// thread and panics handles with (`thread::Result`)[https://doc.rust-lang.org/std/thread/type.Result.html]
/// (depending on whether we are run from inside a suitable runtime), or
/// (`panic::catch_unwind(..)`)[https://doc.rust-lang.org/nightly/std/panic/fn.catch_unwind.html]
/// can be added to this implementation and we may require `panic="unwind"`.
/// See the (book)[https://doc.rust-lang.org/edition-guide/rust-2018/error-handling-and-panics/controlling-panics-with-std-panic.html]
/// and function documentation for more details.
Keeps only entries in a scope for which the filter function returns
`true` and removes the rest.

Conversely, this removes entries in a given scope for which the filter
function returns `false`.
Keeps only entries in a scope for which the filter function returns ` true ` and removes the rest . Conversely this removes entries in a given scope for which the filter function returns ` false ` .
fn retain<F>(&mut self, _filter: F, _scope: Scope)
    where
        F: Fn(&KeyId, &CspSecretKey) -> bool,
    {
        unimplemented!()
    }
fn retain < F > ( & mut self , _filter : F , _scope : Scope ) where F : Fn ( & KeyId , & CspSecretKey ) -> bool , { unimplemented ! ( ) }
Keeps only entries in a scope for which the filter function returns
`true` and removes the rest.
Keeps only entries in a scope for which the filter function returns ` true ` and removes the rest .
&mut self
_filter
F
_scope
Scope
&mut self
_filter
F
_scope
Scope
logs
Implementations SHOULD log the KeyId of any deleted keys
Implementations SHOULD log the KeyId of any deleted keys
panics
This MAY panic if the predicate panics.

Unlike e.g.
This MAY panic if the predicate panics . Unlike e . g .