'Forces Solr to write the index data to disk.
Optionally accepts ``expungeDeletes``. Default is ``None``.
Optionally accepts ``waitFlush``. Default is ``None``.
Optionally accepts ``waitSearcher``. Default is ``None``.
Optionally accepts ``softCommit``. Default is ``False``.
Usage::
solr.commit()'

def commit(self, softCommit=False, waitFlush=None, waitSearcher=None, expungeDeletes=None, handler=u'update'):

    if (expungeDeletes is not None):
        msg = (u'<commit    expungeDeletes="%s"    />' % str(bool(expungeDeletes)).lower())
    else:
        msg = u'<commit    />'
    return self._update(msg, commit=(not softCommit), softCommit=softCommit, waitFlush=waitFlush, waitSearcher=waitSearcher, handler=handler)
