def keys(self):
result = []<EOL>if self.fresh_index is not None:<EOL><INDENT>result += list(self.fresh_index.keys())<EOL><DEDENT>if self.opt_index is not None:<EOL><INDENT>result += list(self.opt_index.keys())<EOL><DEDENT>return result<EOL>
Return ids of all indexed documents.