Does a '_sre.SRE_Pattern' have state,or is it thread-safe?

[John Nagle]

    '_sre.SRE_Pattern' is what "re.compile" returns.

    Is that a mutable object, with state that changes
during the parse, or is it an immutable constant?  Can
two threads use the same '_sre.SRE_Pattern' at the same time?

    (I'm writing something to find race conditions in existing code,
which is why all these obscure introspection-related questions.)

				John Nagle