code: def test_convert_to():
      A = Quantity("A")
      A.set_global_relative_scale_factor(S.One, ampere)
  
      Js = Quantity("Js")
      Js.set_global_relative_scale_factor(S.One, joule * second)
  
      mksa = UnitSystem((m, kg, s, A), (Js,))
      assert (
          convert_to(Js, mksa._base_units)
          == m**2 * kg * s**-1 / 1000
      )
  
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 3 for calling a global function with example usage: test_convert_to() without return types