* Validate **complex structures**:
    * Use of hierarchical Pydantic models, Python `typing`’s `List` and `Dict`, etc.
    * And validators allow complex data schemas to be clearly and easily defined, checked and documented as JSON Schema.
    * You can have deeply **nested JSON** objects and have them all validated and annotated.
* **Extensible**:

     *
     * <p><b>Note:</b> in general, code should assume that the string form returned by {@code
     * ToStringHelper} for a given object may change. In particular, the list of types which are
     * checked for emptiness is subject to change. We currently check {@code CharSequence}s, {@code
     * Collection}s, {@code Map}s, optionals (including Guava's), and arrays.
     *
     * @since 33.4.0
     */

     *
     * <p><b>Note:</b> in general, code should assume that the string form returned by {@code
     * ToStringHelper} for a given object may change. In particular, the list of types which are
     * checked for emptiness is subject to change. We currently check {@code CharSequence}s, {@code
     * Collection}s, {@code Map}s, optionals (including Guava's), and arrays.
     *
     * @since 33.4.0
     */

    /*
     * Inputs are <every possible 10-character string of characters "a./">
     *
     * Expected outputs are generated by the code itself, but they've been
     * checked against the inputs under Bash in order to confirm that the two
     * forms are equivalent (though not necessarily minimal, though we hope this
     * to be the case). Thus, this test is more of a regression test.
     *

    /*
     * Inputs are <every possible 10-character string of characters "a./">
     *
     * Expected outputs are generated by the code itself, but they've been
     * checked against the inputs under Bash in order to confirm that the two
     * forms are equivalent (though not necessarily minimal, though we hope this
     * to be the case). Thus, this test is more of a regression test.
     *

                    }
                }

                // TODO should this be inside the above check?
                // touch file so that this is not checked again until interval has passed
                if (file.exists()) {
                    file.setLastModified(System.currentTimeMillis());
                }
            }
        }

        try {

                 * we read one of the fields declared in that class.
                 */
                Set<Integer> unused = graph.successors(first);
                return null; // so the lambda is a Callable to propagate checked await() exceptions
              }));
    }

    // For more about this test, see the equivalent in AbstractNetworkTest.
    for (Future<?> future : futures.build()) {
      future.get();
    }

      return this;
    }

    private void add(@Nullable Object[] elements, int n) {
      ensureRoomFor(n);
      /*
       * The following call is not statically checked, since arraycopy accepts plain Object for its
       * parameters. If it were statically checked, the checker would still be OK with it, since
       * we're copying into a `contents` array whose type allows it to contain nulls. Still, it's

		if output[0] == "" {
			// spurious blank caused by Split on "\n"
			output = output[1:]
			continue
		}
		t.Errorf("unexpected output: %q", output[0])
		output = output[1:]
	}

	// Checked printing.
	// Now check machine code layout.

	top := pList.Firstpc
	var text *obj.LSym
	ok = true
	ctxt.DiagFunc = func(format string, args ...any) {
		t.Errorf(format, args...)
		ok = false
	}

These custom validators are for things that can be checked with **only** the **same data** provided in the request.

///

### Understand that Code { #understand-that-code }