content: """
  Plotting functions.
  """
  
  from __future__ import absolute_import
  import matplotlib.pyplot as plt
  import numpy as np
  
  
  def hhist(items, title=None, axislabel=None, color=None, height=None, width=None, reverse=False):
      """
      Plots a horizontal histogram of values and frequencies.
  
      Arguments:
          items (iterable[any])     => A list of objects.
          title (Optional[str])     => A title for the resulting histogram.
          axislabel (Optional[str]) => A label for the y-axis that lists the unique items in 
                                       the parameter list.
          color (Optional[str])     => A matplotlib color value for coloring the histogram 
                                       (default: matplotlib's default plot color, a royal blue)
          height (Optional[int])    => A height for the plot (default: 10)
          width (Optional[int])     => A width for the plot (default: 20)
          reverse (Optional[bool])  => Whether or not the histogram should plot from top to bottom in 
                                       order of decreasing frequency or the reverse of that.
  
      Returns:
          Void, but a matplotlib figure should be produced (type=None).
      """
  
      # Parse the unique items and their counts.
      unique_items, item_counts = np.unique(items, return_counts=True)
  
      # Sort the items by frequency.
      item_counts, unique_items = zip(*sorted(zip(item_counts, unique_items), reverse=reverse))
  
      # Plot the frequencies.
      pos = np.arange(len(unique_items)) + 0.5
      plt.figure(figsize=((width or 20), (height or 10)))
      plt.barh(pos, item_counts, align='center', color=color)
      plt.yticks(pos, unique_items)
      plt.xlabel('Frequency')
      if axislabel:
          plt.ylabel(axislabel)
      if title:
          plt.title(title)
  
      plt.show()
  
  