def extract_turn_10_more(df):
    """
    Given a concise conversation dataframe, extract those with 10 or more dialog turns.

    Arg:
        df: A conversation dataframe from a subreddit.
    Return:
        turn_10_more: A dataframe containing only those conversations with 10 or more turns.
    """
    turn_dist = df.groupby('conversation id').size()
    turn_dist_10_more_index = turn_dist[turn_dist >= 10].index
    turn_10_more = df[df['conversation id'].isin(list(turn_dist_10_more_index))]
    
    return turn_10_more