input: Write a python function to plot a graph representing the ASCII values of characters in a given string.
  assert plot_ascii_graph("Hello World!") == None
  assert plot_ascii_graph("Python") == None
  assert plot_ascii_graph("Data Science") == None
output: def plot_ascii_graph(s):
      import matplotlib.pyplot as plt
  
      characters = list(s)
      ascii_values = [ord(char) for char in characters]
  
      plt.figure(figsize=(10, 5))
      plt.bar(characters, ascii_values, color='blue')
      plt.xlabel('Characters')
      plt.ylabel('ASCII Values')
      plt.title('ASCII Values of Characters in the String')
      plt.show()