You're seeing just the callback before_dispatch, go back to Cqrs.Command module for more information.
Link to this callback

before_dispatch(command, keyword)

View Source


before_dispatch(command(), keyword()) :: {:ok, command()} | {:error, any()}

This callback is intended to be used as a last chance to do any validation that performs IO.

This callback is optional.

Invoked before handle_dispatch/2.