Typing: timestepper module

[skim0119]

Type-hinting timestepper module

-> % mypy --config-file pyproject.toml elastica/timestepper
Success: no issues found in 5 source files

• Partially address Type hints and static type checking for PyElastica #255

New Protocols

• elastica/system/protocol.py: generic protocol for all SystemType
  • Also includes SymplecticSystemProtocol and ExplicitSystemProtocol
• elastica/timestepper/protocol.py:
  • generic protocol for any StepperProtocol
    • Extended protocols: StatefulStepperProtocol
  • MethodCollectorProtocol for class that generates operators.
  • MemoryProtocol for state representation of timesteppers. (unused)

Refactoring

• Unused __init__, args, and kwargs are removed.
• SymplecticStepperTag and ExplicitStepperTag are now in tag.py
  • All stepper tagging are now done using elastica.timestepper.tag.tag.
• In testing, some MockRod and MockRigidBody was created using TypeAlias, which is not an intended usage. It is refactored to import original base classes.

Minor changes

• isinstance is safer type-comparison instead of type(...) == type(...)
• Change some float types to np.floating
  • Not sure yet this is a good idea. Maybe we should make generic datatype: FLOAT: TypeAlias = float | np.floating.
• Some commented-out by string is replaced with proper python-commenting for better syntax highlighitng.

[armantekinalp]

LGTM nice work @skim0119