Add some more failing cases to unit tests for the

brackets checking.  I had simply carried over what was there
before, but it really seemed insufficient...

stix2patterns/test/test_helpers.py

@@ -20,5 +20,14 @@ def test_brackets_check(value):
  assert brackets_check(value)
 
 
-def test_brackets_check_fail():
+@pytest.mark.parametrize(
+ "value", [
+ None,
+ "file:size = 1280",
+ "(file:size = 1280)",
+ " ( file:size = 1280 ) ",
+ " (( (( file:size = 1280 ) )) ) ",
+ ]
+)
+def test_brackets_check_fail(value):
  assert not brackets_check(None)