EvaluationDataset.save_as('csv'/'jsonl') 在重新加载时会将包含 '|' 的上下文项分割开来

Describe the bug

EvaluationDataset.save_as("csv") and save_as("jsonl") flatten context and retrieval_context into a single |-delimited cell. A | inside an item is not escaped, so the matching loaders split that item apart on reload. One chunk comes back as several items, some of them empty or whitespace only. No exception and no warning is raised. save_as("json") is unaffected.