lxml_prettyprint.py

# create a new parser object
parser = etree.XMLParser(remove_blank_text=True)

# when we parse the input file, add a parser argument
tree = etree.parse("path/to/ead.xml", parser=parser)

[... making edits ...]

# when making the output string, add a new pretty_print argument
ead_text = etree.tostring(tree, pretty_print=True, xml_declaration=True, encoding="utf-8")

# write the file
with open(os.path.join("path/to/ead/directory", "ead_filename.xml"), mode="w") as f:
  f.write(ead_text)