<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def handle(self, request):
 """Handle an HTTP request for executing an API call. This method authenticates the request checking its signature, and then calls the C{execute} method, passing it a L{Call} object set with the principal for the authenticated user and the generic parameters extracted from the request. @param request: The L{HTTPRequest} to handle. """

        request.id = str(uuid4())
        deferred = maybeDeferred(self._validate, request)
        deferred.addCallback(self.execute)

        def write_response(response):
            request.setHeader("Content-Length", str(len(response)))
            request.setHeader("Content-Type", self.content_type)
            # Prevent browsers from trying to guess a different content type.
            request.setHeader("X-Content-Type-Options", "nosniff")
            request.write(response)
            request.finish()
            return response

        def write_error(failure):
            if failure.check(APIError):
                status = failure.value.status

                # Don't log the stack traces for 4xx responses.
                if status < 400 or status >= 500:
                    log.err(failure)
                else:
                    log.msg("status: %s message: %s" % (
                        status, safe_str(failure.value)))

                body = failure.value.response
                if body is None:
                    body = self.dump_error(failure.value, request)
            else:
                # If the error is a generic one (not an APIError), log the
                # message , but don't send it back to the client, as it could
                # contain sensitive information. Send a generic server error
                # message instead.
                log.err(failure)
                body = "Server error"
                status = 500
            request.setResponseCode(status)
            write_response(body)

        deferred.addCallback(write_response)
        deferred.addErrback(write_error)
        return deferred