[Python] What's the difference between Pint's "Quantity" and "PlainQuantity"?

My IDE (type-checking provided by the Pyright language server) doesn't like me passing pint.Quantity instances to functions type-hinted with pint.Quantity:

from pint import Quantity

def get_units(quantity: Quantity):
return quantity.units

get_unit(Quantity(value=1, units="m")) # IDE complains here


My language server says this:

Argument of type "PlainQuantity[Any]" cannot be assigned
to parameter "quantity" of type "Quantity" in function
"get_unit" [E]


My questions are: what is PlainQuantity? Why does Quantity not return an instance of Quantity? Am I doing something wrong?

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