docs: def time_entries(self, start_date=None, end_date=None):
          '''Array of all time entries'''
          if self.cache['time_entries']: return self.cache['time_entries']
          if not start_date:
              start_date = datetime.date(1900, 1, 1)
          if not end_date:
              end_date = datetime.date.today()
          time_entry_xml = self.bc.list_time_entries(self.id, start_date, end_date)
          time_entries = []
          for entry in ET.fromstring(time_entry_xml).findall("time-entry"):
              time_entries.append(TimeEntry(entry))
          self.cache['time_entries'] = time_entries
          return self.cache['time_entries']