How to use the numexpr.expressions.FuncNode function in numexpr

kind = 'double'
                    r = multiply(r, OpNode('sqrt', [a], kind))
                if r is None:
                    r = OpNode('ones_like', [a])
                if x < 0:
                    r = OpNode('div', [ConstantNode(1), r])
                return r
        if get_optimization() in ('moderate', 'aggressive'):
            if x == -1:
                return OpNode('div', [ConstantNode(1), a])
            if x == 0:
                return OpNode('ones_like', [a])
            if x == 0.5:
                kind = a.astKind
                if kind in ('int', 'long'): kind = 'double'
                return FuncNode('sqrt', [a], kind=kind)
            if x == 1:
                return a
            if x == 2:
                return OpNode('mul', [a, a])
    return OpNode('pow', [a, b])

def _func(a, axis=None):
        axis = encode_axis(axis)
        if isinstance(a, ConstantNode):
            return a
        if isinstance(a, (bool, int_, long_, float, double, complex)):
            a = ConstantNode(a)
        return FuncNode(name, [a, axis], kind=a.astKind)
    return _func

def where_func(a, b, c):
    if isinstance(a, ConstantNode):
        return b if a.value else c
    if allConstantNodes([a, b, c]):
        return ConstantNode(numpy.where(a, b, c))
    return FuncNode('where', [a, b, c])

def contains_func(a, b):
    return FuncNode('contains', [a, b], kind='bool')

if allConstantNodes(args):
            return ConstantNode(func(*[x.value for x in args]))
        kind = commonKind(args)
        if kind in ('int', 'long'):
            # Exception for following NumPy casting rules
            #FIXME: this is not always desirable. The following
            # functions which return ints (for int inputs) on numpy
            # but not on numexpr: copy, abs, fmod, ones_like
            kind = 'double'
        else:
            # Apply regular casting rules
            if minkind and kind_rank.index(minkind) > kind_rank.index(kind):
                kind = minkind
            if maxkind and kind_rank.index(maxkind) < kind_rank.index(kind):
                kind = maxkind
        return FuncNode(func.__name__, args, kind)