def get_columns_list(self):
columns = list(self.obj._fields.keys())<EOL>if "<STR_LIT>" in columns:<EOL><INDENT>columns.remove("<STR_LIT>")<EOL><DEDENT>return columns<EOL>
modified: removing the '_cls' column added by Mongoengine to support
mongodb document inheritance
cf. http://docs.mongoengine.org/apireference.html#documents:
"A Document subclass may be itself subclassed,
to create a specialised version of the document that will be
stored in the same collection.
To facilitate this behaviour a _cls field is added to documents
(hidden though the MongoEngine interface).
To disable this behaviour and remove the dependence on the presence of _cls set
allow_inheritance to False in the meta dictionary."