docs: byte[][] getQualifierKeys(String family) {
  		Map<String, TypeInformation<?>> qualifierMap = familyMap.get(family);
  
  		if (qualifierMap == null) {
  			throw new IllegalArgumentException("Family " + family + " does not exist in schema.");
  		}
  		Charset c = Charset.forName(charset);
  
  		byte[][] qualifierKeys = new byte[qualifierMap.size()][];
  		int i = 0;
  		for (String name : qualifierMap.keySet()) {
  			qualifierKeys[i++] = name.getBytes(c);
  		}
  		return qualifierKeys;
  	}