code: public static OClass probeOClass(Iterator<ODocument> it, int probeLimit) {
  		return getCommonOClass(Iterators.limit(it, probeLimit));
  	}
docs: Check first several items to resolve common {@link OClass}
  @param it {@link Iterable} over {@link ODocument}s
  @param probeLimit limit over iterable
  @return common {@link OClass} or null