How to import effects explicitly in PureScript?

MainNG.purs

-- This is not OK.

module MainNG where

import Prelude (Unit)
import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)

main :: forall eff. Eff (console :: CONSOLE | eff) Unit
main = log "Hi"

-- Error:
-- Error in module Main:
-- Error at  line 6, column 1 - line 7, column 1:
--   Unknown type class Control.Monad.Eff.Eff
-- See https://github.com/purescript/purescript/wiki/Error-Code-UnknownTypeClass for more information, or to contribute content related to this error.

MainOK.purs

-- This is OK.

module MainOK where

import Prelude
import Control.Monad.Eff
import Control.Monad.Eff.Console

main :: forall eff. Eff (console :: CONSOLE | eff) Unit
main = log "Hi"

Solution.purs

module Solution where

import Prelude (Unit())
import Control.Monad.Eff (Eff())
import Control.Monad.Eff.Console (CONSOLE(), log)

main :: forall eff. Eff (console :: CONSOLE | eff) Unit
main = log "Hi"

import Control.Monad.Eff (Eff())

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