update loader and test to handle lines with brackets

tests/test_utils.py

diff --git a/tests/test_utils.py b/tests/test_utils.py
index e68f6a7..a9bb6a8 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -369,6 +369,7 @@
     vector_data = textwrap.dedent("""
 
         # http://tools.ietf.org/html/rfc1321
+        [irrelevant]
 
         Len = 0
         Msg = 00