A vulnerability version range can be:
the literal string (any)
empty string (equivalent to (any))
single
single, single
single, single, single
single, single, single, single
etc.
A single vulnerability version range can be:
version
>version
>=version
<version
<=version
>version <version
>=version <version
>version <=version
>=version <=version
The format of version is defined by the feed type.