class Net::SSH::Connection::SingleSessionEventLoop

def ev_preprocess(&block)

we call block with session as argument
Compatibility for original single session event loops: 
def ev_preprocess(&block)
  return false if block_given? && !yield(@sessions.first)
  @sessions.each(&:ev_preprocess)
  return false if block_given? && !yield(@sessions.first)
  return true
end