def output_asg_cpu(dates=None, values=None, asg_name=None, output_type=None):
    """
    @type dates: list
    @type values: list
    @type asg_name: unicode
    @type output_type: unicode
    """
    try:
        import matplotlib.pyplot as plt
        import matplotlib.dates as mdates
    except ImportError:
        exit('matplotlib required to output graphs.')
    if output_type in ('graph', None):
        plt.subplots_adjust(bottom=0.2)
        plt.xticks(rotation=25)
        ax = plt.gca()
        xfmt = mdates.DateFormatter('%Y-%m-%d %H:%M:%S')
        ax.xaxis.set_major_formatter(xfmt)
        plt.plot(dates, values)
        plt.gcf().autofmt_xdate()
        plt.title('CPU statistics for: {0}'.format(asg_name))
        plt.xlabel('Time (UTC)')
        plt.ylabel('CPU %')
        plt.grid()
        plt.ylim([0, 100])
        plt.show()
        exit(0)
