code: @Override
  	public IPAddress assignPrefixForSingleBlock() {
  		Integer newPrefix = getPrefixLengthForSingleBlock();
  		return newPrefix == null ? null : setPrefixLength(newPrefix, false);
  	}
docs: Returns the equivalent CIDR address with a prefix length for which the address subnet block matches the range of values in this address.
  <p>
  If no such prefix length exists, returns null.
  <p>
  
  Examples:<br>
  1.2.3.4 returns 1.2.3.4/32<br>
  1.2.*.* returns 1.2.0.0/16<br>
  1.2.*.0/24 returns 1.2.0.0/16 <br>
  1.2.*.4 returns null<br>
  1.2.252-255.* returns 1.2.252.0/22<br>
  1.2.3.4/x returns the same address<br>
  
  @return