docs: def convert_ts(tt):
      '''
      tt: time.struct_time(tm_year=2012, tm_mon=10, tm_mday=23, tm_hour=0,
      tm_min=0, tm_sec=0, tm_wday=1, tm_yday=297, tm_isdst=-1)
  
      >>> tt = time.strptime("23.10.2012", "%d.%m.%Y")
      >>> convert_ts(tt)
      1350950400
  
      tt: time.struct_time(tm_year=1513, tm_mon=1, tm_mday=1, tm_hour=0,
      tm_min=0, tm_sec=0, tm_wday=2, tm_yday=1, tm_isdst=0)
  
      >>> tt = time.strptime("1.1.1513", "%d.%m.%Y")
      >>> convert_ts(tt)
      0
      >>> tt = 12
      >>> convert_ts(tt)
      '''
      try:
          ts = calendar.timegm(tt)
  
          '''
          As from the github issue https://github.com/prashanthellina/rsslurp/issues/680,
          there are some cases where we might get timestamp in negative values, so consider
          0 if the converted timestamp is negative value.
          '''
          if ts < 0: ts = 0
      except TypeError:
          ts = None
      return ts