content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.apache.beam.sdk.values;
  
  import java.util.Map;
  import org.apache.beam.sdk.Pipeline;
  
  /**
   * The interface for things that might be input to a {@link
   * org.apache.beam.sdk.transforms.PTransform}.
   */
  public interface PInput {
    /** Returns the owning {@link Pipeline} of this {@link PInput}. */
    Pipeline getPipeline();
  
    /**
     * Expands this {@link PInput} into a list of its component output {@link PValue PValues}.
     *
     * <ul>
     *   <li>A {@link PValue} expands to itself.
     *   <li>A tuple or list of {@link PValue PValues} (such as {@link PCollectionTuple} or {@link
     *       PCollectionList}) expands to its component {@code PValue PValues}.
     * </ul>
     *
     * <p>Not intended to be invoked directly by user code.
     */
    Map<TupleTag<?>, PValue> expand();
  }
  