This function attempts to reserve a job from one of the tubes that a Tube
object is currently watching. Note that the return type for the function
is a Nullable!Job. This value will test as null if a Job did not become
available before the time out.
The maximum number of seconds for the server to wait for a
job to become available. If no job is available then the
function will return null. If set to zero the function will
block indefinitely (i.e. it won't time out).
This function attempts to reserve a job from one of the tubes that a Tube object is currently watching. Note that the return type for the function is a Nullable!Job. This value will test as null if a Job did not become available before the time out.