spec says "pr" must appear exactly once in microdesc, but it does not appear in recent microdescs in collector
the dir-auth spec says:
"pr" SP Entries NL
[Exactly once.]
The "proto" element as specified in section 2.1.1.
[Before Tor 0.4.5.1-alpha, this field was optional.]
but recent microdecriptors seems to all lack this value.
The router status entries only mark this field as At most once