VintageNet.PowerManager.start_powering_off

You're seeing just the callback start_powering_off, go back to VintageNet.PowerManager module for more information.
Link to this callback

start_powering_off(state)

View Source

Specs

start_powering_off(state :: any()) ::
  {:ok, next_state :: any(), time_to_power_off :: non_neg_integer()}

Start powering off the hardware for a network interface

This function should start a graceful shutdown of the network interface hardware. It may return immediately. The return value specifies how long in seconds VintageNet should wait before calling power_off/2. The idea is that a graceful power off should be allowed some time to complete, but not forever.