'Try to guess if the file is a InChI file.
>>> from galaxy.datatypes.sniff import get_test_fname
>>> fname = get_test_fname(\'drugbank_drugs.inchi\')
>>> InChI().sniff(fname)
True
>>> fname = get_test_fname(\'drugbank_drugs.cml\')
>>> InChI().sniff(fname)
False'

def sniff(self, filename):

    inchi_lines = iter_headers(filename, sep='    ', count=10)
    for inchi in inchi_lines:
        if (not inchi[0].startswith('InChI=')):
            return False
    return True
