<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def getCredentials(self, request):
 """ Derive credentials from an HTTP request. Override SessionWrapper.getCredentials to add the Host: header to the credentials. This will make web-based virtual hosting work. @type request: L{nevow.inevow.IRequest} @param request: The request being handled. @rtype: L{twisted.cred.credentials.1ICredentials} @return: Credentials derived from the HTTP request. """

        username = usernameFromRequest(request)
        password = request.args.get('password', [''])[0]
        return credentials.UsernamePassword(username, password)