default RecordType get(String identifier) throws GuacamoleException {
        return asCollection().stream()
                .filter((record) -> {
                    String recordIdentifier = record.getIdentifier();
                    return recordIdentifier != null && recordIdentifier.equals(identifier);
                })
                .findFirst().orElse(null);
    }
Returns the record having the given unique identifier, if records within
this set have unique identifiers. If records within this set do not have
defined unique identifiers, this function has no effect.

@param identifier
    The unique identifier of the record to retrieve.

@return
    The record having the given unique identifier, or null if there is
    no such record.

@throws GuacamoleException
    If an error occurs while retrieving the record.
guacamole-ext/src/main/java/org/apache/guacamole/net/auth/ActivityRecordSet.java