<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def improve():
 """Disables access to websites that are defined as 'distractors'"""

    with open(settings.HOSTS_FILE, "r+") as hosts_file:
        contents = hosts_file.read()
        if not settings.START_TOKEN in contents and not settings.END_TOKEN in contents:
            hosts_file.write(settings.START_TOKEN + "\n")
            for site in set(settings.DISTRACTORS):
                hosts_file.write("{0}\t{1}\n".format(settings.REDIRECT_TO, site))
                for sub_domain in settings.SUB_DOMAINS:
                    hosts_file.write("{0}\t{1}.{2}\n".format(settings.REDIRECT_TO, sub_domain, site))
            hosts_file.write(settings.END_TOKEN + "\n")

    reset_network("Concentration is now improved :D!")