
*Optional properties:*

``allocation`` : ``<string>``
  Media set allocation policy ('continue', 'always', or a calendar event).
``comment`` : ``<string>``
  Comment.
``encrypt`` : ``<string>``
  Tape encryption key fingerprint (sha256).
``retention`` : ``<string>``
  Media retention policy ('overwrite', 'keep', or time span).
``template`` : ``<string>``
  Media set naming template (may contain strftime() time format specifications).

