code: public static <K, V> Map<K, V> checkNotNullOrEmpty(Map<K, V> arg, String argName) throws NullPointerException,
                                                                                        IllegalArgumentException {
          Preconditions.checkNotNull(arg, argName);
          checkArgument(!arg.isEmpty(), argName, "Cannot be an empty map.");
          return arg;
      }
docs: Throws a NullPointerException if the arg argument is null. Throws an IllegalArgumentException
  if the Map arg argument has a size of zero.
  
  @param <K> The type of keys in the provided map.
  @param <V> The type of keys in the provided map.
  @param arg The argument to check.
  @param argName The name of the argument (to be included in the exception message).
  @return The arg.
  @throws NullPointerException If arg is null.
  @throws IllegalArgumentException If arg is not null, but has a length of zero.