单词:
    params: 形参
    attribute:属性
    argument:实参
    pandas库函数与dataframe私有函数:
    **

    1. pd.merge()
    2. pd.concat()
    1. df.groupby(by=label|list of lale,as_index=False,group_keys=False)
    2. df.sort_values(by='',ascending=False)
    3. df.dropna(subset=[])
    4. df.drop_duplicates(subset=[])
    5. df.set_index(key=str)
    6. df.drop(lables)