How to use the cgt.core.ElwiseUnary function in cgt

def abs(x):
    "Applies function abs elementwise to argument x"
    return core.Result(core.ElwiseUnary("abs"), [x])

def cast(x, dtype):
    dtype = Dtype.canon(dtype)
    if x.dtype == dtype: 
        return x
    else:
        diff = _dtype_kind(dtype) in "cf"
        opname = "castto%s"%dtype
        ui = UnaryInfo(opname, lambda x: x.astype(dtype),diff, dtype, "cast(gy,%s)"%x.dtype if diff else "_no_grad()", "((%s)x)"%np2c[dtype])
        return Result(ElwiseUnary(opname, ui), [x])

def sign(x):
    "Applies function sign elementwise to argument x"
    return core.Result(core.ElwiseUnary("sign"), [x])

def cast(x, dtype):
    """
    Convert variable x to the desired datatype
    """
    x = core.as_node(x)
    if (x.dtype == dtype):
        return x
    else:
        diff = (core.dtype_kind(dtype) in 'cf')
        opname = 'cast_to_%s' % dtype
        ui = core.UnaryInfo(opname, _get_nu_cast(dtype), diff, dtype,  
            lambda x,y,gy : cast(gy, x.dtype) if diff else None, 'x')
        return core.Result(core.ElwiseUnary(opname, ui), [x])

def iceil(x):
    "Applies function iceil elementwise to argument x"
    return core.Result(core.ElwiseUnary("iceil"), [x])

def __neg__(self):
        return Result(ElwiseUnary("neg"), [self])
    # Binary ops

def ceil(x):
    "Applies function ceil elementwise to argument x"
    return core.Result(core.ElwiseUnary("ceil"), [x])

node2shape[node] = node2shape[node.parents[0]][node.op.idx]
    else:
        newparents = node.parents
        node2shape[node] = node.op.shp_apply(newparents)
        # assert all([s.get_dtype() == "i8" for s in node2shape[node]])
    assert len(node2shape[node]) == node.ndim or isinstance(node.get_type(),Tuple)
    # -- SCALAR VALUE --
    if isinstance(node, Result):
        op = node.op
        if isinstance(op, Fill):
            node2sv[node] = op.value
        elif isinstance(op, Constant) and utils.is_singleton(op.value):
            node2sv[node] = op.value.flat[0]
        elif isinstance(op, Repeat) and newparents[0] in node2sv:
            node2sv[node] = node2sv[newparents[0]]
        elif isinstance(op, (ElwiseUnary, ElwiseBinary)) and all(p in node2sv for p in newparents):
            node2sv[node] = node.op.info.pyfunc(*(node2sv[p] for p in newparents))