code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  package org.openqa.selenium.support.ui;
  
  import com.google.common.base.Function;
  import org.openqa.selenium.WebDriver;
  
  /**
   * Models a condition that might reasonably be expected to eventually evaluate to something that is
   * neither null nor false. Examples would include determining if a web page has loaded or that an
   * element is visible.
   *
   * <p>Note that it is expected that ExpectedConditions are idempotent. They will be called in a loop
   * by the {@link WebDriverWait} and any modification of the state of the application under test may
   * have unexpected side-effects.
   *
   * @param <T> The return type
   */
  // NB: this originally extended Guava's Function interface since Java didn't have one. To avoid code
  // such as "com.google.common.base.Function condition = ExpectedConditions.elementFound(By);"
  // breaking at compile time, we continue to extend Guava's Function interface.
  public interface ExpectedCondition<T>
      extends Function<WebDriver, T>, java.util.function.Function<WebDriver, T> {}
  