fix cpython json encoding of nan

fixedjson.py

# this is a hack to fix https://github.com/python/cpython/issues/70293
from json import JSONEncoder 

class FixedNaNJSONEncoder(JSONEncoder):
    def iterencode(self, o, _one_shot=False):
        # fix cpython json encoding of nan values
        # see https://github.com/python/cpython/issues/98306
        # this overrides JSON.enconder.iterencode by trading performance for correctness
        markers = {}
        _encoder = encode_basestring

        _default = self.default
        INFINITY = float('inf')
        _inf = INFINITY
        _neginf = -INFINITY

        def floatstr(o, **kwargs):
            if o != o:
                text = 'null'
            elif o == _inf:
                text = 'Infinity'
            elif o == _neginf:
                text = '-Infinity'
            else:
                return repr(o)
            return text

        _iterencode = _make_iterencode(
            markers, self.default, _encoder, self.indent, floatstr,
            self.key_separator, self.item_separator, self.sort_keys,
            self.skipkeys, _one_shot)
        return _iterencode(o, 0)