def add(self, data, key=None):
        """Add field values to container.

        :param dict data: Serialized values for field
        :param str key: Optional key; if not provided, values will be added
            to `self.payload`.

        """
        sink = self.options[key] if key is not None else self.data
        for key, value in iteritems(data):
            sink.add(key, value)
Add field values to container.

        :param dict data: Serialized values for field
        :param str key: Optional key; if not provided, values will be added
            to `self.payload`.

        
robobrowser/forms/form.py