code: def get_usage(self, loadbalancer=None, start=None, end=None):
          
          if start is end is None:
              period = None
          else:
              parts = []
              startStr = utils.iso_time_string(start)
              if startStr:
                  parts.append("startTime=%s" % startStr)
              endStr = utils.iso_time_string(end)
              if endStr:
                  parts.append("endTime=%s" % endStr)
              period = "&".join(parts).strip("&")
          if loadbalancer is None:
              uri = "/loadbalancers/usage"
          else:
              uri = "/loadbalancers/%s/usage" % utils.get_id(loadbalancer)
          if period:
              uri = "%s?%s" % (uri, period)
          resp, body = self.api.method_get(uri)
          return body
docs: Return the load balancer usage records for this account. If 'loadbalancer'
          is None, records for all load balancers are returned. You may optionally
          include a start datetime or an end datetime, or both, which will limit
          the records to those on or after the start time, and those before or on the
          end time. These times should be Python datetime.datetime objects, Python
          datetime.date objects, or strings in the format: "YYYY-MM-DD HH:MM:SS" or
          "YYYY-MM-DD".