@Override
  public final int previousIndex() {
    return backingIterator().previousIndex();
  }

  @Override
  public void set(@ParametricNullness T element) {
    throw new UnsupportedOperationException();
  }

  @Override
  public void add(@ParametricNullness T element) {
    throw new UnsupportedOperationException();
  }

            return parent.get(index);
        }

        public E set(final int index, final E element) {
            return parent.set(index, element);
        }

        public void add(final int index, final E element) {
            parent.add(index, element);
        }

        public E remove(final int index) {
            return parent.remove(index);
        }

	</li>
	<li>An element list that does not contain any keys must
	    list an element for each struct field in the
	    order in which the fields are declared.
	</li>
	<li>If any element has a key, every element must have a key.
	</li>
	<li>An element list that contains keys does not need to
	    have an element for each struct field. Omitted fields

		scheme = strings.ToLower(proto)
	} else if proto := r.Header.Get(forwarded); proto != "" {
		// match should contain at least two elements if the protocol was
		// specified in the Forwarded header. The first element will always be
		// the 'for=', which we ignore, subsequently we proceed to look for
		// 'proto=' which should precede right after `for=` if not

    /**
     * Gets the configuration key for the minimum size constraint.
     * @return name of size the element must be higher or equal to
     */
    String minKey() default StringUtil.EMPTY;

    /**
     * Gets the configuration key for the maximum size constraint.
     *
     * @return name of size the element must be lower or equal to
     */
    String maxKey() default StringUtil.EMPTY;

  public void testPoll_size1() {
    assertEquals("size1Queue.poll() should return first element", e0(), getQueue().poll());
    expectMissing(e0());
  }

  @CollectionFeature.Require({KNOWN_ORDER, SUPPORTS_REMOVE})
  @CollectionSize.Require(SEVERAL)
  public void testPoll_sizeMany() {
    assertEquals("sizeManyQueue.poll() should return first element", e0(), getQueue().poll());
    expectMissing(e0());
  }

## Composition by architecture modules

Each [architecture module and platform](platforms.md) can contribute code to any of the elements.
Not every module contributes to every element.

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * The annotated element must not be null.
 * <p>
 * Annotated fields must not be null after construction has completed.
 * <p>
 * When this annotation is applied to a method it applies to the method return value.
 *
 * @see Nullable

            return getOtherLocation(key);
        }
    } // -- InputLocation getLocation( Object )

    /**
     * Gets the map of nested element locations within this location.
     *
     * @return a map of keys to InputLocation instances for nested elements, or null if none
     */
    public java.util.Map<Object, InputLocation> getLocations() {
        return locations;

     */
    ParameterizedClassDesc[] getParameterizedClassDescs();

    /**
     * Returns the element type if the parameter type of the method is a parameterized {@link Collection}.
     *
     * @param index
     *            The index of the parameter
     * @return The element type if the parameter type is a parameterized {@link Collection}, otherwise {@literal null}
     */