Task.child_spec
You're seeing just the function
child_spec, go back to Task module for more information.
Specs
child_spec(term()) :: Supervisor.child_spec()
Returns a specification to start a task under a supervisor.
arg is passed as the argument to Task.start_link/1 in the :start field
of the spec.
For more information, see the Supervisor module,
the Supervisor.child_spec/2 function and the Supervisor.child_spec/0 type.