Migrate.opt.period: def of bend-kit-migrate@0.3.0.0
Import: import bend-kit-migrate@0.3.0.0/migrate.bend as Migrate
Lines 508-516 of bend-kit-migrate@0.3.0.0/migrate.bend: https://jend.leeeet.dev/read.txt?path=bend-kit-migrate@0.3.0.0/migrate.bend&start_line=508&end_line=516

import Base

# An absent v2 period is monthly.
def opt.period(m: Maybe<&1, Scalar>) -> Result<&1, &1, Error, Period>:
  match m:
    case None{}:
      Done{Monthly{}}
    case Some{SStr{b}}:
      name.period(Tag.of(b))
    case Some{s}:
      Fail{BadField{KPeriod{}}}

Uses (8):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Result
  https://jend.leeeet.dev/definition.txt?path=bend-kit-migrate@0.3.0.0/migrate.bend&name=Error
  https://jend.leeeet.dev/definition.txt?path=bend-kit-migrate@0.3.0.0/migrate.bend&name=Key
  https://jend.leeeet.dev/definition.txt?path=bend-kit-migrate@0.3.0.0/migrate.bend&name=Period
  https://jend.leeeet.dev/definition.txt?path=bend-kit-migrate@0.3.0.0/migrate.bend&name=Scalar
  https://jend.leeeet.dev/definition.txt?path=bend-kit-migrate@0.3.0.0/migrate.bend&name=Tag.of
  https://jend.leeeet.dev/definition.txt?path=bend-kit-migrate@0.3.0.0/migrate.bend&name=name.period