class Net::IMAP::ThreadMember


by Net::IMAP#thread.
Net::IMAP::ThreadMember represents a thread-node returned

def all_seqnos(node = self) 

def all_seqnos(node = self)
  [node.seqno].concat node.children.flat_map { _1.all_seqnos }
end

def to_sequence_set

recursively.
Returns a SequenceSet containing #seqno and all #children's seqno, 
def to_sequence_set
  SequenceSet.new all_seqnos
end