code: def from_T050017(cls, url, coltype = LIGOTimeGPS):
  		
  		match = cls._url_regex.search(url)
  		if not match:
  			raise ValueError("could not convert %s to CacheEntry" % repr(url))
  		observatory = match.group("obs")
  		description = match.group("dsc")
  		start = match.group("strt")
  		duration = match.group("dur")
  		if start == "-" and duration == "-":
  			# no segment information
  			segment = None
  		else:
  			segment = segments.segment(coltype(start), coltype(start) + coltype(duration))
  		return cls(observatory, description, segment, url)
docs: Parse a URL in the style of T050017-00 into a CacheEntry.
  		The T050017-00 file name format is, essentially,
  
  		observatory-description-start-duration.extension
  
  		Example:
  
  		>>> c = CacheEntry.from_T050017("file://localhost/data/node144/frames/S5/strain-L2/LLO/L-L1_RDS_C03_L2-8365/L-L1_RDS_C03_L2-836562330-83.gwf")
  		>>> c.observatory
  		'L'
  		>>> c.host
  		'localhost'
  		>>> os.path.basename(c.path)
  		'L-L1_RDS_C03_L2-836562330-83.gwf'