私のコード
tree = ET.Element('e')
tree.attrib['u'] = 'F' + str(srh) + '_0'
if procedural_variables:
    pvs = ET.SubElement(tree, 'pvs')
    for procedural_variable in procedural_variables:
        pv = ET.SubElement(pvs, 'pv')
        n = ET.SubElement(pv, 'n')
        n.text = procedural_variable['name']
        v = ET.SubElement(pv, 'v')
        v.text = str(procedural_variable['value'])
ET.dump(tree)
どうすればこれtreeをいくつかとして書くことができますかfile.xml?