def get_row_by_fsid(self, fs_id):
for row in self.liststore:<EOL><INDENT>if row[FSID_COL] == fs_id:<EOL><INDENT>return row<EOL><DEDENT><DEDENT>return None<EOL>
确认在Liststore中是否存在这条任务. 如果存在, 返回TreeModelRow,
        否则就返回None