Correct file write

- Correct bug in file write

fattura_elettronica_reader/api.py

@@ -431,7 +431,7 @@ def patch_invoice_schema_file(invoice_schema_file: str, offending_line: str,
 
     .. note: this sucks. A better solution needs to be found.
     """
-    save = list()
+    save: list = list()
     with open(invoice_schema_file, 'r') as f:
         for line in f:
             if line == offending_line:
@@ -442,7 +442,7 @@ def patch_invoice_schema_file(invoice_schema_file: str, offending_line: str,
     with tempfile.NamedTemporaryFile('w', delete=False) as f:
         f.flush()
         os.fsync(f.fileno())
-        f.write(save)
+        f.write(os.linesep.join(save))
     shutil.move(f.name, invoice_schema_file)