"""Returns the last N lines of text data, handling various edge cases and errors.

This function processes the input string to extract the last N lines, where N is specified by the `n_str` argument. It handles type validation, negative values, and invalid inputs gracefully, returning appropriate error messages when necessary.

Args:
    current_data: The input data as a string. If not a string, an error is returned.
    n_str: A string representing the number of lines (N) to extract from the end of `current_data`.
    mime_type: The original MIME type of the data, which is passed through unchanged.
    log_id: An identifier used for logging purposes.

Returns:
    Tuple[Any, Optional[str], Optional[str]]: A tuple containing:
        - result_data: A string with the last N lines of `current_data`. If N is 0, an empty string is returned.
        - original_mime_type: The original MIME type passed in as `mime_type`.
        - error_string: An error message if any validation or processing error occurs; otherwise, None.

Raises:
    This function does not raise exceptions but returns error messages as part of the tuple.
"""