This function checks if the `measure_id` column is present in both input dataframes `hces_df` and `conv_fct_df`. If `measure_id` is not present in either of the dataframes, the function throws an error. The function then filters out rows in `hces_df` that are not in `conv_fct_df` based on the `measure_id` column. It returns a dataframe `missing_conv_fct_df` that contains the missing `measure_id` values.