AMQPHelpers.Adapter.set_channel_options

You're seeing just the callback set_channel_options, go back to AMQPHelpers.Adapter module for more information.
Link to this callback

set_channel_options(channel, options)

Specs

set_channel_options(channel :: AMQP.Channel.t(), options :: keyword()) ::
  :ok | {:error, any()}

Sets the message prefetch count or prefetch size.

See AMQP.Basic.qos/2.