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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def raster(event_times_list, color='k'):
 """ Creates a raster from spike trains. @param event_times_list (array) matrix containing times in which a cell fired @param color (string) color of spike in raster @return ax (int) position of plot axes """

  ax = plt.gca()
  for ith, trial in enumerate(event_times_list):
    plt.vlines(trial, ith + .5, ith + 1.5, color=color)
  plt.ylim(.5, len(event_times_list) + .5)
  return ax