Test modify cone
==================

>>> from PyNormaliz import NmzCone, NmzResult, NmzModifyCone
>>> C = NmzCone(cone=[[1,0],[0,1]])
>>> NmzResult(C,"HilbertBasis") == [[0, 1], [1, 0]]
True
>>> NmzModifyCone(C,"cone",[[-1,0]])
True
>>> NmzResult(C,"HilbertBasis") == [[0, 1]]
True