def __getitem__(self, key):
if isinstance(key, (int, np.integer)):<EOL><INDENT>return self.get_by_index(key)<EOL><DEDENT>else:<EOL><INDENT>return self.get_by_id(key)<EOL><DEDENT>
Simple interface for querying the database.

        Depending on whether key is an integer or not, look up a gene set
        either by index, or by ID.