Use of None datatype and __new__ method for subclass instantiation

Let us have this example:

use kB from ase.units
use exp from numpy

kB_ = 1 [ eV/K ] * kB
ene = (v: 0.1, 0.05) [eV]
temperature = 273.15 [K]

beta = 1.0/(kB_*temperature)
print(sum(map((e: exp(-e*beta)), ene)))

The first error I get is

Traceback (most recent call last):
  File "/home/vanjo/work/vre-language/examples/../scripts/run_model.py", line 34, in <module>
    main()
  File "/home/vanjo/work/vre-language/src/virtmat/language/utilities/errors.py", line 70, in wrapper
    process_error(err)
  File "/home/vanjo/work/vre-language/src/virtmat/language/utilities/errors.py", line 52, in process_error
    raise err.__cause__
  File "/home/vanjo/work/vre-language/src/virtmat/language/utilities/errors.py", line 22, in wrapper
    return func(*args, **kwargs)
  File "/home/vanjo/work/vre-language/src/virtmat/language/interpreter/instant_executor.py", line 373, in func_reduce_value
    return self.type_(ret)
  File "/usr/lib/python3.10/functools.py", line 981, in __get__
    val = self.func(instance)
  File "/home/vanjo/work/vre-language/src/virtmat/language/constraints/typechecks.py", line 466, in sum_type
    assert issubclass(self.parameter.type_.datatype, (int, float))
TypeError: issubclass() arg 1 must be a class

After fixing this by adding if datatype is not None: before the block calling issubclass I get this result:

0.13381515446825232 dimensionless

It is correct by dimensionless should not be printed due to the formatter. This becomes more obvious after adding

s = sum(map((e: exp(-e*beta)), ene))
print(s*kB_)

with the output:

1.1531293901786782e-05 dimensionless [electron_volt / kelvin]

After debugging the types I found out that the class <class 'virtmat.language.constraints.typechecks.Number'> produced by DType metaclass is used for casting the output after evaluation of sum taking a pint.Quantity as and returns an object containing a pint.Quantity as a magnitude! This is not due to the special metaclass but the behavior of all pint.Quantity subclasses - this can be reproduced by simply subclassing pint.Quantity to MyQuantity and then taking MyQuantity(pint.Quantity(1)).magnitude. The way to solve this is to write __new__ method of MyQuantity to override the default __new__ method.