from enum import Enum class UnitDensity(str, Enum): """ The valid types for density units. """ # noqa: E501 """# Pounds per cubic feet. """ # noqa: E501 LB_FT3 = 'lb:ft3' """# Kilograms per cubic meter. """ # noqa: E501 KG_M3 = 'kg:m3' def __str__(self) -> str: return str(self.value)