if (conflict != null) {
        broken = entry;
        // We're definitely going to throw, but we'll try to keep the BiMap in an internally
        // consistent state by removing the bad entry.
        itr.remove();
      }
    }
    if (broken != null) {
      throw new IllegalArgumentException("value already present: " + broken.getValue());
    }
  }

  @Override

  }

  @Override
  protected Map<K, V> delegate() {
    return delegate;
  }

  /** Returns its input, or throws an exception if this is not a valid key. */
  @CanIgnoreReturnValue
  @ParametricNullness
  K checkKey(@ParametricNullness K key) {
    return key;
  }

  /** Returns its input, or throws an exception if this is not a valid value. */
  @CanIgnoreReturnValue
  @ParametricNullness