fix: render ListElement in mixed lists with empty key column

Previously ListElement had no to_markdown() method, crashing when a list
mixed dict items (- x: 123) and plain strings (- y). Now plain string
items render as a table row with an empty key and the value shown.
Closes #27.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Chris1221

test/test_examples.py

@@ -248,6 +248,8 @@ def test_mixed_list_does_not_crash(self):
         # Regression test for issue #27
         output = get_output("test/yaml/mixed_list.yaml")
         self.assertIn("a_list_of_mixed_dict_and_str", output)
+        self.assertIn("123", output)
+        self.assertIn("`y`", output)
 
 
 class TestPackage(unittest.TestCase):

yamldoc/entries.py

@@ -82,7 +82,7 @@ def __repr__(self):
 
     def non_excluded_entries(self):
         """Returns a list of entries that are not excluded."""
-        return [entry for entry in self.entries if not entry.exclude and not isinstance(entry, ListElement)]
+        return [entry for entry in self.entries if not entry.exclude]
 
     def table_header(self, schema=False):
         if schema:
@@ -149,7 +149,13 @@ def to_markdown(self, schema=False):
 @dataclass
 class ListElement:
     entry: str
-    exclude: bool = False 
+    exclude: bool = False
+
+    def to_markdown(self, schema=False):
+        if schema:
+            return f"|  | `{self.entry}` | Unknown |  |"
+        else:
+            return f"|  | `{self.entry}` |  |"
 
 
 class Entry: