message: refactor(api): Add todo comments calling out some TransferPlan questions
diff: @@ -364,6 +364,9 @@ class TransferPlan:
  volume,
  sources,
  dests,
  + # todo(mm, 2021-03-10):
  + # Refactor to not need an InstrumentContext, so we can more
  + # easily test this class's logic on its own.
  instr: 'InstrumentContext',
  max_volume: float,
  api_version: APIVersion,
  @@ -546,6 +549,9 @@ class TransferPlan:
  # the other maintains consistency in default behaviors of all functions
  plan_iter = self._expand_for_volume_constraints(
  self._volumes, self._dests,
  + # todo(mm, 2021-03-09): Is it right for this to be
  + # _instr_.max_volume? Does/should this take the tip maximum volume
  + # into account?
  self._instr.max_volume
  - self._strategy.disposal_volume
  - self._strategy.air_gap)
  @@ -640,6 +646,9 @@ class TransferPlan:
  .. Aspirate -> .....*
  """
  plan_iter = self._expand_for_volume_constraints(
  + # todo(mm, 2021-03-09): Is it right to use _instr.max_volume here?
  + # Why don't we account for tip max volume, disposal volume, or air
  + # gap?
  self._volumes, self._sources, self._instr.max_volume)
  current_xfer = next(plan_iter)
  if self._strategy.new_tip == types.TransferTipPolicy.ALWAYS:
  