Add version field to data saver/ loader metadata about hamilton HOT 2 OPEN

def get_dataframe_metadata(df: pd.DataFrame, metadata_func: Optional[Callable[[pd.DataFrame], Dict[str, Any]]] = None) -> Dict[str, Any]:
    """Gives metadata from loading a dataframe.

    Note: we reserve the right to change this schema. So if you're using this come
    chat so that we can make sure we don't break your code.

    This will default to include:
    - the number of rows
    - the number of columns
    - the column names
    - the data types
    
    If you provide an override, then your DataFrame will be passed into that 
    Callable and the resulting Dictionary will include your custom metadata.
    """
    if metadata_func is not None:
        return {DATAFRAME_METADATA: metadata_func(df)}
    else:
        return {
            DATAFRAME_METADATA: {
                "rows": len(df),
                "columns": len(df.columns),
                "column_names": list(df.columns),
                "datatypes": [str(t) for t in list(df.dtypes)],  # for serialization purposes
            }
        }