'Determines whether the file is XML or not
>>> from galaxy.datatypes.sniff import get_test_fname
>>> fname = get_test_fname( \'megablast_xml_parser_test1.blastxml\' )
>>> GenericXml().sniff( fname )
True
>>> fname = get_test_fname( \'interval.interval\' )
>>> GenericXml().sniff( fname )
False'

def sniff(self, filename):

    handle = open(filename)
    line = handle.readline()
    handle.close()
    return line.startswith('<?xml    ')
