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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 generate_html():
 """ Generate an HTML file incorporating the images produced by this script """

    html_file = open(html_filename, "w")
    html_file.write("<html><body>")
    html_file.write("<h1>Here are some graphs for you!</h1>")
    for image in [lines_filename, bars_filename, histogram_filename]:
        html_file.write("<div><h2>{0}</h2><img src='{0}' /></div>".format(image))
    html_file.write("</body></html>")
    html_file.close()