The method mutates the input dictionary directly by modifying set_opts in place. This can lead to unexpected side effects if the caller retains a reference to the original dictionary. Consider creating a new dictionary instead of modifying the input. For example, you could initialize a new dictionary result = {} and populate it in the loop, then return result instead of set_opts.

When converting values to strings, Python boolean values will be rendered as "True" or "False" (capitalized). However, Docker Buildx expects lowercase boolean values ("true", "false") in set options. This affects both the dictionary values in line 203 and the else branch in line 205. Consider adding special handling for boolean values: str(v).lower() if isinstance(v, bool) else str(v) to ensure proper formatting for Docker.

The new _set_opts_dict_to_str method lacks test coverage. Given that the repository has comprehensive test coverage for similar methods (as seen in test_bake.py with tests for other BakePlan methods), consider adding tests to verify the correct conversion of different data types (lists, dicts, strings, numbers, booleans) to their string representations. This is especially important since this method handles the critical task of formatting parameters for Docker Buildx Bake.

The join operation assumes all list items are strings. If the list contains non-string types (e.g., numbers, booleans), this will raise a TypeError. Consider converting list items to strings: ",".join(str(item) for item in data). Note that boolean values should be lowercased for Docker compatibility, so you may need ",".join(str(item).lower() if isinstance(item, bool) else str(item) for item in data).