BUG: unyt_quantity are Sized objects without a length ?

[neutrinoceros]

• unyt version: 2.8.0
• Python version: 3.9.6
• Operating System: OS/X

Description

unyt_quantity objects are recognised as instances of collections.abc.Sized, which indicates that they have a __len__� protocol. However, calling len(quantity) fails with an error message contradicting this.

What I Did

from collections.abc import Sized
import unyt as un

quan = un.unyt_quantity(1, "cm")
assert isinstance(quan, Sized)
print(len(quan))

output

TypeError: len() of unsized object

[neutrinoceros]

So there would be two concurrent approaches to solving this. The first possibility would be to make all quantities have len 1.
Since quand[0] returns an error too however, I suppose that the issue is really that isinstance(quan, Sized) evaluates as True, which is likely a direct consequence of inheriting from unyt_array

[neutrinoceros]

Turns out this isn't specific to unyt but is generally true with numpy 0d ndarrays.