/** Constructor for the header node. */
    AvlNode() {
      this.elem = null;
      this.elemCount = 1;
    }

    // For discussion of pred() and succ(), see the comment on the pred and succ fields.

    private AvlNode<E> pred() {
      return requireNonNull(pred);
    }

    private AvlNode<E> succ() {
      return requireNonNull(succ);
    }

        Pattern pattern,
        UnsignedInteger ui,
        UnsignedLong ul,
        StringBuilder sb,
        Predicate<?> pred,
        Function<?, ?> func,
        Object obj) {
      delegate.foo(
          s, r, n, it, b, eq, e, in, c, ord, charset, unit, cls, joiner, pattern, ui, ul, sb, pred,
          func, obj);
    }

    @Override
    public String toString() {
      return delegate.toString();
    }

        Pattern pattern,
        UnsignedInteger ui,
        UnsignedLong ul,
        StringBuilder sb,
        Predicate<?> pred,
        Function<?, ?> func,
        Object obj) {
      delegate.foo(
          s, r, n, it, b, eq, e, in, c, ord, charset, unit, cls, joiner, pattern, ui, ul, sb, pred,
          func, obj);
    }

    @Override
    public String toString() {
      return delegate.toString();
    }

			continue
		}
	}
	pred := func(c rune) bool { return c == 'X' }
	var fieldsFuncTests = []FieldsTest{
		{"", []string{}},
		{"XX", []string{}},
		{"XXhiXXX", []string{"hi"}},
		{"aXXbXXXcX", []string{"a", "b", "c"}},
	}
	for _, tt := range fieldsFuncTests {
		b := []byte(tt.s)
		a := FieldsFunc(b, pred)

		// Appending to the results should not change future results.