我定義了一個如下所示的函數：def incident_rate(substation,year,events):    age = conductor_yearly_df.loc[conductor_yearly_df['SUBSTATION']==substation,conductor_yearly_df.columns.str.contains(year)].reset_index(drop=True).values[0][0]    length = conductor_yearly_df.loc[conductor_yearly_df['SUBSTATION']==substation,conductor_yearly_df.columns.str.contains(year)].reset_index(drop=True).values[0][1]    temp = events / (age * length)     return temp當我在代碼中調用該函數時（例如：incident_rate('WB',2019,6)，它會拋出以下錯誤：TypeError: first argument must be string or compiled pattern我不確定我在哪里犯了錯誤。誰能指導我如何解決錯誤？