codec_options = collections.codec_options
    if DataFrame is not None:

        from bson.codec_options import TypeRegistry, TypeCodec
        from pandas import NA
        class PandasNanCodec(TypeCodec):
            python_type = NA.__class__
            bson_type = None
            def transform_python(self, value):
                """Function that transforms a custom type value into a type
                that BSON can encode."""
                return None

            def transform_bson(self, value):
                """Function that transforms a vanilla BSON type value into our
                custom type."""
                return NA

        type_registry = TypeRegistry([PandasNanCodec()])
        codec_options = codec_options.with_options(type_registry=type_registry)