<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def upload(self, filename, number_of_hosts):
 """Upload the given file to the specified number of hosts. :param filename: The filename of the file to upload. :type filename: str :param number_of_hosts: The number of hosts to connect to. :type number_of_hosts: int :returns: A list of dicts with 'host_name' and 'url' keys for all successful uploads or an empty list if all uploads failed. :rtype: list """

        return self.multiupload(filename, self.random_hosts(number_of_hosts))