def update_headers(self, dictionary, keys=None):
        """
        Updates the header with the supplied dictionary. If keys=None, it
        will be unsorted. Otherwise it will loop over the supplied keys
        (a list) in order.
        """
        if keys is None: keys = list(dictionary.keys())
        for k in keys: self.insert_header(k, dictionary[k])
        return self
Updates the header with the supplied dictionary. If keys=None, it
        will be unsorted. Otherwise it will loop over the supplied keys
        (a list) in order.