def getYadisXRD(xrd_tree):
 xrd = None
 for xrd in xrd_tree.findall(xrd_tag):
  pass
 if (xrd is None):
  raise XRDSError('No XRD present in tree')
 return xrd

def getYadisXRD ( xrd_tree ) : xrd = None for xrd in xrd_tree . findall ( xrd_tag ) : pass if ( xrd is None ) : raise XRDSError ( 'No XRD present in tree' ) return xrd
return the xrd element that should contain the yadis services .