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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def to_lal_unit(aunit):
 """Convert the input unit into a `LALUnit` For example:: m^2 kg^-4 Parameters aunit : `~astropy.units.Unit`, `str` the input unit Returns ------- unit : `LALUnit` the LALUnit representation of the input Raises ------ ValueError if LAL doesn't understand the base units for the input """

    if isinstance(aunit, string_types):
        aunit = units.Unit(aunit)
    aunit = aunit.decompose()
    lunit = lal.Unit()
    for base, power in zip(aunit.bases, aunit.powers):
        # try this base
        try:
            lalbase = LAL_UNIT_FROM_ASTROPY[base]
        except KeyError:
            lalbase = None
            # otherwise loop through the equivalent bases
            for eqbase in base.find_equivalent_units():
                try:
                    lalbase = LAL_UNIT_FROM_ASTROPY[eqbase]
                except KeyError:
                    continue
        # if we didn't find anything, raise an exception
        if lalbase is None:
            raise ValueError("LAL has no unit corresponding to %r" % base)
        lunit *= lalbase ** power
    return lunit