:type modulators: list of Modulator
        :return:

def write_modulators_to_project_file(self, tree=None):
        """
        :type modulators: list of Modulator
        :return:
        """
        if self.project_file is None or not self.modulators:
            return

        if tree is None:
            tree = ET.parse(self.project_file)

        root = tree.getroot()
        root.append(Modulator.modulators_to_xml_tag(self.modulators))

        tree.write(self.project_file)