This method Validates, gets the Python value, checks unique indexes, 
        gets the db value, and then returns the prepared doc dict object. 
        Useful for save and backup functions.
        @param doc_obj: 
        @return:

def prep_doc(self, doc_obj):
        """
        This method Validates, gets the Python value, checks unique indexes, 
        gets the db value, and then returns the prepared doc dict object. 
        Useful for save and backup functions.
        @param doc_obj: 
        @return: 
        """
        doc = doc_obj._data.copy()
        for key, prop in list(doc_obj._base_properties.items()):
            prop.validate(doc.get(key), key)
            raw_value = prop.get_python_value(doc.get(key))
            if prop.unique:
                self.check_unique(doc_obj, key, raw_value)
            value = prop.get_db_value(raw_value)
            doc[key] = value

        doc['_doc_type'] = get_doc_type(doc_obj.__class__)
        return doc