def __neg__(self):
        """x.__neg__() <==> -x"""

        A = self.A.copy()
        for key in self.keys:
            A[key] = -A[key]
        return Poly(A, self.dim, self.shape, self.dtype)
def __neg__ ( self ) : A = self . A . copy ( ) for key in self . keys : A [ key ] = - A [ key ] return Poly ( A , self . dim , self . shape , self . dtype )
x.__neg__() <==> -x