[Python] Store derived units without prefix while avoiding unit to base

I am new to Pint. I am dealing with derived units such as Siemens, Joule, Farad etc. In particular, I would like to store the created quantities with their units without any prefix, without converting to the base units. For example, 1 millisiemens (mS) should be stored as 0.001 S.

Let's try to explain this with an example. The following code snippet:

import pint

ureg = pint.UnitRegistry(system="mks")
quantity = ureg.Quantity(1, ureg.Unit("mm")) # Define quantity of 1 millimiter
stored_quantity = quantity.to_base_units()
print(stored_quantity) # print: 0.001 meter OK


In this case, I get the desired effect, the quantity stored is in meter. But when I try with derived quantities, Pint converts it to the base units, or (using others to_xxx method) it preserves the derived quantity but also the prefix. Let's see with an example:

quantity = ureg.Quantity(1, ureg.Unit("mJ"))
print(quantity) # 1 millijoule
print(quantity.to_root_units()) # 1.0 gram * meter ** 2 / second ** 2
print(quantity.to_base_units()) # 0.001 kilogram * meter ** 2 / second ** 2
print(quantity.to_reduced_units()) # 1 millijoule -> Preserves derived unit but also "milli"
print(quantity.to_compact()) # 1 millijoule -> Preserves derived unit but also "milli"


The desired output should be 0.001 J.

Of course, one could explicitly call:

stored_quantity = quantity.to(ureg.joule),

but I couldn't find a way to get the information of ureg.joule programmatically. Is there a way to achieve this goal?

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