import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.function.BiFunction;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A general-purpose bimap implementation using any two backing {@code Map} instances.
 *
 * <p>Note that this class contains {@code equals()} calls that keep it from supporting {@code

import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A general-purpose bimap implementation using any two backing {@code Map} instances.
 *
 * <p>Note that this class contains {@code equals()} calls that keep it from supporting {@code