}

  /**
   * A function from an input to a result.
   *
   * @param <T> the type of the input to the function
   * @param <U> the type of the result of the function
   */
  public interface ClosingFunction<T extends @Nullable Object, U extends @Nullable Object> {

    /**
     * Applies this function to an input, or throws an exception if unable to do so.
     *

Then, the arguments of the call are <i>passed</i> to the function,
which means that they are <a href="#Assignment_statements">assigned</a>
to their corresponding function parameters,
and the called function begins execution.
The return parameters of the function are passed
back to the caller when the function returns.
</p>

<p>
Calling a <code>nil</code> function value
causes a <a href="#Run_time_panics">run-time panic</a>.

      Function<? super F, T> function, Supplier<F> supplier) {
    return new SupplierComposition<>(function, supplier);
  }

  private static final class SupplierComposition<
          F extends @Nullable Object, T extends @Nullable Object>
      implements Supplier<T>, Serializable {
    final Function<? super F, T> function;
    final Supplier<F> supplier;

      Function<? super F, T> function, Supplier<F> supplier) {
    return new SupplierComposition<>(function, supplier);
  }

  private static final class SupplierComposition<
          F extends @Nullable Object, T extends @Nullable Object>
      implements Supplier<T>, Serializable {
    final Function<? super F, T> function;
    final Supplier<F> supplier;

   * {@link java.util.stream.Collectors#toMap(java.util.function.Function,
   * java.util.function.Function) Collectors.toMap(Function, Function)}, which throws an {@code
   * IllegalStateException}.)
   *
   * @since 21.0
   */
  public static <T extends @Nullable Object, K extends Enum<K>, V>
      Collector<T, ?, ImmutableMap<K, V>> toImmutableEnumMap(
          java.util.function.Function<? super T, ? extends K> keyFunction,

   * the collection operation is performed. (This differs from the {@code Collector} returned by
   * {@link java.util.stream.Collectors#toMap(java.util.function.Function,
   * java.util.function.Function) Collectors.toMap(Function, Function)}, which throws an {@code
   * IllegalStateException}.)
   *
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */

   */
  public final <T extends @Nullable Object> FluentIterable<T> transform(
      Function<? super E, T> function) {
    return from(Iterables.transform(getDelegate(), function));
  }

  /**
   * Applies {@code function} to each element of this fluent iterable and returns a fluent iterable
   * with the concatenated combination of results. {@code function} returns an Iterable of results.
   *

   */
  public final <T extends @Nullable Object> FluentIterable<T> transform(
      Function<? super E, T> function) {
    return from(Iterables.transform(getDelegate(), function));
  }

  /**
   * Applies {@code function} to each element of this fluent iterable and returns a fluent iterable
   * with the concatenated combination of results. {@code function} returns an Iterable of results.
   *

import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertThrows;

import com.google.common.base.Equivalence;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.base.Joiner;
import com.google.common.base.Predicate;
import com.google.common.collect.Ordering;
import com.google.common.primitives.UnsignedInteger;

import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertThrows;

import com.google.common.base.Equivalence;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.base.Joiner;
import com.google.common.base.Predicate;
import com.google.common.collect.Ordering;
import com.google.common.primitives.UnsignedInteger;