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T3833.hs:10:1: error:
    • Can't make a derived instance of ‘Monoid (DecodeMap e)’:
        ‘Monoid’ is not a stock derivable class (Eq, Show, etc.)
        Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
    • In the stand-alone deriving instance for ‘Monoid (DecodeMap e)’