unquote.ex

defmodule ModuleToBeUsed do
  defmacro __using__(_) do
    IO.puts __MODULE__ # COMPILATION STAGE
    quote do # needed to prevent execution on compilation stage
      IO.inspect(__MODULE__, label: "__MODULE__")
      IO.inspect(unquote(__MODULE__), label: "unquote(__MODULE__)")
      import unquote(__MODULE__)
      def test, do: IO.puts "I am test" # EXECUTION STAGE
    end
  end
end

defmodule ModuleUsing do
  use ModuleToBeUsed

  def test_of_test, do: test() # I can call `test` here!
end

ModuleUsing.test_of_test()

####### output ########
# Elixir.ModuleToBeUsed
# __MODULE__: ModuleUsing
# unquote(__MODULE__): ModuleToBeUsed
# I am test

https://stackoverflow.com/questions/41231482/what-does-import-unquote-module-do-in-a-using-callback