'Return True if the operand is negative; otherwise return False.
>>> ExtendedContext.is_signed(Decimal(\'2.50\'))
False
>>> ExtendedContext.is_signed(Decimal(\'-12\'))
True
>>> ExtendedContext.is_signed(Decimal(\'-0\'))
True
>>> ExtendedContext.is_signed(8)
False
>>> ExtendedContext.is_signed(-8)
True'

def is_signed(self, a):

    a = _convert_other(a, raiseit=True)
    return a.is_signed()
