'Return the difference between the two operands.
>>> ExtendedContext.subtract(Decimal(\'1.3\'), Decimal(\'1.07\'))
Decimal(\'0.23\')
>>> ExtendedContext.subtract(Decimal(\'1.3\'), Decimal(\'1.30\'))
Decimal(\'0.00\')
>>> ExtendedContext.subtract(Decimal(\'1.3\'), Decimal(\'2.07\'))
Decimal(\'-0.77\')
>>> ExtendedContext.subtract(8, 5)
Decimal(\'3\')
>>> ExtendedContext.subtract(Decimal(8), 5)
Decimal(\'3\')
>>> ExtendedContext.subtract(8, Decimal(5))
Decimal(\'3\')'

def subtract(self, a, b):

    a = _convert_other(a, raiseit=True)
    r = a.__sub__(b, context=self)
    if (r is NotImplemented):
        raise TypeError(('Unable    to    convert    %s    to    Decimal' % b))
    else:
        return r
