Creates a new content property. Potentially a duplicate at the REST API level of
        create_new_property.
        :param content_id (string): A string containing the id of the property content container.
        :param new_property_data (dict): A dictionary describing the new property for the content. Must have the keys
                                         "key" and "value".
        :param callback: OPTIONAL: The callback to execute on the resulting data, before the method returns.
                         Default: None (no callback, raw data returned).
        :return: The JSON data returned from the content/{id}/property endpoint,
                 or the results of the callback. Will raise requests.HTTPError on bad input, potentially.

        Example property data:
        {
            "key": "example-property-key",
            "value": {
                "anything": "goes"
            }
        }

def create_new_content_property(self, content_id, content_property, callback=None):
        """
        Creates a new content property. Potentially a duplicate at the REST API level of
        create_new_property.
        :param content_id (string): A string containing the id of the property content container.
        :param new_property_data (dict): A dictionary describing the new property for the content. Must have the keys
                                         "key" and "value".
        :param callback: OPTIONAL: The callback to execute on the resulting data, before the method returns.
                         Default: None (no callback, raw data returned).
        :return: The JSON data returned from the content/{id}/property endpoint,
                 or the results of the callback. Will raise requests.HTTPError on bad input, potentially.

        Example property data:
        {
            "key": "example-property-key",
            "value": {
                "anything": "goes"
            }
        }
        """
        assert isinstance(content_property, dict)
        assert {"key", "value"} <= set(content_property.keys())
        return self._service_post_request("rest/api/content/{id}/property".format(id=content_id),
                                          data=json.dumps(content_property),
                                          headers={"Content-Type": "application/json"}, callback=callback)