old_contents: import matplotlib.pyplot as plt
  from matplotlib.dates import DateFormatter
  
  class PlotUtil:
      @classmethod
      def ploting(xvals, yvals, xlabel_str, ylabel_str, title, style, label, grid=True):
          """
          creates a plot of time series data
          """
          # close all old plots
          plt.close("all")
          # plotting
          fig, ax = plt.subplots()
          fig.set_size_inches(12,3.5) # you can set it to 15, 3.5 to make the cell width longer
          ax.plot_date(xvals, yvals, style, label=label)
  
          handles, labels = ax.get_legend_handles_labels()
          ax.legend(handles, labels)
  
          myFormatter = DateFormatter("%H:%M")
          ax.xaxis.set_major_formatter(myFormatter)
          plt.xlabel(xlabel_str)
          plt.ylabel(ylabel_str)
          plt.title(title)
          # show the grid line/ help line in plot
          plt.grid(grid)
          #plt.legend(loc='upper right')
          #plt.axis([0, 210, 0, 0.04 ])
          #plt.figure(figsize=[9,6])
          plt.show()
new_contents: import matplotlib.pyplot as plt
  from matplotlib.dates import DateFormatter
  
  class PlotUtil:
      # TODO: need be tested , still buggy
      @classmethod
      def ploting(xvals, yvals, xlabel_str, ylabel_str, title, style, label, grid=True):
          """
          creates a plot of time series data
  
          """
          # close all old plots
          plt.close("all")
          # plotting
          fig, ax = plt.subplots()
          fig.set_size_inches(12,3.5) # you can set it to 15, 3.5 to make the cell width longer
          ax.plot_date(xvals, yvals, style, label=label)
  
          handles, labels = ax.get_legend_handles_labels()
          ax.legend(handles, labels)
  
          myFormatter = DateFormatter("%H:%M")
          ax.xaxis.set_major_formatter(myFormatter)
          plt.xlabel(xlabel_str)
          plt.ylabel(ylabel_str)
          plt.title(title)
          # show the grid line/ help line in plot
          plt.grid(grid)
          #plt.legend(loc='upper right')
          #plt.axis([0, 210, 0, 0.04 ])
          #plt.figure(figsize=[9,6])
          plt.show()
subject: add todo docs