<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def getUnitRegistry(length="meter", time="second", substance="item", volume=None, other=()):
 """Return a pint.UnitRegistry made compatible with ecell4. Parameters length : str, optional A default unit for '[length]'. 'meter' is its default. time : str, optional A default unit for '[time]'. 'second' is its default. substance : str, optional A default unit for '[substance]' (the number of molecules). 'item' is its default. volume : str, optional A default unit for '[volume]'. Its default is None, thus '[length]**3'. other : tuple, optional A list of user-defined default units other than the above. Returns ------- ureg : pint.UnitRegistry """

    ureg = pint.UnitRegistry()
    ureg.define('item = mole / (avogadro_number * 1 mole)')

    try:
        pint.molar
    # except UndefinedUnitError:
    except AttributeError:
        # https://github.com/hgrecco/pint/blob/master/pint/default_en.txt#L75-L77
        ureg.define('[concentration] = [substance] / [volume]')
        ureg.define('molar = mol / (1e-3 * m ** 3) = M')

    base_units = [unit for unit in (length, time, substance, volume) if unit is not None]
    base_units.extend(other)
    _ = ureg.System.from_lines(
        ["@system local using international"] + base_units,
        ureg.get_base_units)
    ureg.default_system = 'local'

    wrap_quantity(ureg.Quantity)

    pint.set_application_registry(ureg)  # for pickling
    return ureg