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• Could not deduce (Semigroup (Maybe' a))
    arising from the superclasses of an instance declaration
  from the context: Monoid a
    bound by the instance declaration
    at /home/alex/prj/ByLanguage/all_haskell_prj/stepik/haskell_1/test-new/src/Lib.hs:9:10-38
• In the instance declaration for ‘Monoid (Maybe' a)’typecheck(-Wdeferred-type-errors)

Noncanonical ‘mappend’ definition detected
in the instance declaration for ‘Monoid (Maybe' a)’.
‘mappend’ will eventually be removed in favour of ‘(<>)’
Either remove definition for ‘mappend’ (recommended) or define as ‘mappend = (<>)’
See also: https://gitlab.haskell.org/ghc/ghc/-/wikis/proposal/semigroup-monoidtypecheck(-Wnoncanonical-monoid-instances)