Construct a line graph using the data from this dataframe, where the x-axis is years and the y-axis is the columns 2015 2016 2017 2018 2019 0 5.375734 5.382185 5.354019 5.375917 5.407096

import matplotlib.pyplot as plt
def linegraph(df):
  plt.plot(df.index, df['2015'], label = "2015")
  plt.plot(df.index, df['2016'], label = "2016")
  plt.plot(df.index, df['2017'], label = "2017")
  plt.plot(df.index, df['2018'], label = "2018")
  plt.plot(df.index, df['2019'], label = "2019")
  plt.legend()
  plt.show()

linegraph(df)