Improve type annotations for core.(trajectory/units)

[DanielYang59]

Summary

• Improve type annotations for core.trajectory and core.units
• Nest _get_si_unit and _check_mappings inside the only methods that call them in Unit

Extend the following to support argument "unit" as both str and Unit

• __init/new__ of FloatWithUnit and ArrayWithUnit
• get_conversion_factor of Unit, and to methods of FloatWithUnit and ArrayWithUnit

The type hint suggests str, docstring suggest Unit and implementation seems to handle partially of both.

pymatgen/pymatgen/core/units.py

Lines 295 to 305 in bb68c78

	def __init__(self, val: float | Number, unit: str, unit_type: str | None = None) -> None:
	"""Initialize a float with unit.
	Args:
	val (float): Value
	unit (Unit): A unit. e.g. "C".
	unit_type (str): A type of unit. e.g. "charge"
	"""
	if unit_type is not None and str(unit) not in ALL_UNITS[unit_type]:
	raise UnitError(f"{unit} is not a supported unit for {unit_type}")
	self._unit = Unit(unit)

Might be good to support both for more flexibility, without sacrificing backwards compatibility.

[DanielYang59]

Can I have this one reviewed please? @janosh

[janosh]

thanks @DanielYang59! 👍

[DanielYang59]

Thanks for reviewing! Appreciate that.