old_contents: import pandas as pd
  
  def split_uber_data(filename):
      """
      A function split the data/time of Uber data set.
  
      Parameter: Uber data file, month
      """
      df = pd.read_csv(filename, sep=',', header=0)
  
      # process the Data/Time column
      time = pd.DatetimeIndex(df['Date/Time'])
      df['year'] = time.year
      df['month'] = time.month
      df['day'] = time.day
      df['dayofweek'] = time.dayofweek
      df['hour'] = time.hour
      df['minute'] = time.minute
      df['time'] = time.time
  
      # converts the data frame to csv file
      df.to_csv("split_" + filename, index=False)
  
  
  def split_taxi_data(filename):
      """
      A function split the data/time of Uber data set.
  
      Parameter: taxi data file, month
      """
      df = pd.read_csv(filename, sep=',', header=0)
  
      # process the Data/Time column
      time = pd.DatetimeIndex(df.icol(0))
      df['year'] = time.year
      df['month'] = time.month
      df['day'] = time.day
      df['dayofweek'] = time.dayofweek
      df['hour'] = time.hour
      df['minute'] = time.minute
      df['time'] = time.time
  
      # converts the data frame to csv file
      df.to_csv("split_" + filename, index=False)
new_contents: import pandas as pd
  import os
  
  def split_uber_data(file_name):
      """
      A function split the data/time of Uber data set.
  
      Parameter: Uber data file, month
  
      Return: True or False for unittest purpose
              True, the output file saved
              False, the output file fail to saved
      """
  
      df = pd.read_csv(file_name, sep=',', header=0)
  
      # process the Data/Time column
      time = pd.DatetimeIndex(df['Date/Time'])
      df['year'] = time.year
      df['month'] = time.month
      df['day'] = time.day
      df['dayofweek'] = time.dayofweek
      df['hour'] = time.hour
      df['minute'] = time.minute
      df['time'] = time.time
  
      # converts the data frame to csv file
      df.to_csv("split_" + file_name, index=False)
  
      # return True or False for unittest purpose
      if os.path.exists("split_" + file_name):
          return True
      else :
          return False
  
  
  def split_taxi_data(file_name):
      """
      A function split the data/time of Uber data set.
  
      Parameter: taxi data file, month
      """
      df = pd.read_csv(file_name, sep=',', header=0)
  
      # process the Data/Time column
      time = pd.DatetimeIndex(df.icol(0))
      df['year'] = time.year
      df['month'] = time.month
      df['day'] = time.day
      df['dayofweek'] = time.dayofweek
      df['hour'] = time.hour
      df['minute'] = time.minute
      df['time'] = time.time
  
      # converts the data frame to csv file
      df.to_csv("split_" + file_name, index=False)
  
      # return True or False for unittest purpose
      if os.path.exists("split_" + file_name):
          return True
      else :
          return False
  
subject: Add return value for unittest purpose