code: def test_get_units_non_prefixed():
      from sympy.physics.units import volt, ohm
  
      unit_system = UnitSystem.get_unit_system("SI")
      units = unit_system.get_units_non_prefixed()
      for prefix in [
          "giga",
          "tera",
          "peta",
          "exa",
          "zetta",
          "yotta",
          "kilo",
          "hecto",
          "deca",
          "deci",
          "centi",
          "milli",
          "micro",
          "nano",
          "pico",
          "femto",
          "atto",
          "zepto",
          "yocto",
      ]:
          for unit in units:
              assert isinstance(
                  unit, Quantity
              ), f"{unit} must be a Quantity, not {type(unit)}"
              assert (
                  not unit.is_prefixed
              ), f"{unit} is marked as prefixed"
              assert (
                  not unit.is_physical_constant
              ), f"{unit} is marked as physics constant"
              assert not unit.name.name.startswith(
                  prefix
              ), f"Unit {unit.name} has prefix {prefix}"
      assert volt in units
      assert ohm in units
  
file_path: sympy/sympy/physics/units/tests/test_unitsystem.py
imports: from sympy.physics.units import DimensionSystem, joule, second, ampere
  from sympy.core.numbers import Rational
  from sympy.core.singleton import S
  from sympy.physics.units.definitions import c, kg, m, s
  from sympy.physics.units.definitions.dimension_definitions import length, time
  from sympy.physics.units.quantities import Quantity
  from sympy.physics.units.unitsystem import UnitSystem
  from sympy.physics.units.util import convert_to
label_desc: Use image node_id 7 for calling a global function with example usage: test_get_units_non_prefixed() without return types