code: def fetch(path,fromTime,untilTime=None,now=None):
    
    fh = None
    try:
      fh = open(path,'rb')
      return file_fetch(fh, fromTime, untilTime, now)
    finally:
      if fh:
        fh.close()
docs: fetch(path,fromTime,untilTime=None)
  
  path is a string
  fromTime is an epoch time
  untilTime is also an epoch time, but defaults to now.
  
  Returns a tuple of (timeInfo, valueList)
  where timeInfo is itself a tuple of (fromTime, untilTime, step)
  
  Returns None if no data can be returned