AMQPHelpers.Adapter.open_channel

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

open_channel(connection)

Specs

open_channel(connection :: AMQP.Connection.t()) ::
  {:ok, AMQP.Channel.t()} | {:error, term()}

Opens a new channel in a previously opened connection.

See AMQP.Channel.open/2.