new_contents: def prepare_step(x, y):
      '''
      Prepare data for a nice step plot.
  
      Args:
          x (list):   List concaining bin edges.
          y (list):   List containing bin values.
  
      Returns:
          x (list):   List containing corrected bin edges.
          y (list):   List containing corrected bin values.
      '''
      if type(x) is not list: 
          x = x.tolist()
      if type(y) is not list:
          y = y.tolist()
  
      y.insert(0, y[0])
      x.insert(0, x[0])
      y.insert(0, 0)
      x.append(x[-1])
      y.append(0)
      
      return x, y
  
subject: add utils.py with usefull functions