return (reader instanceof BufferedReader)
        ? (BufferedReader) reader
        : new BufferedReader(reader);
  }

  /**
   * Opens a new {@link Stream} for reading text one line at a time from this source. This method
   * returns a new, independent stream each time it is called.
   *
   * <p>The returned stream is lazy and only reads from the source in the terminal operation. If an

        try (BufferedReader br = new BufferedReader(readerSupplier.open(), BUFFER_SIZE)) {
            br.mark(BUFFER_SIZE);
            XMLStreamReader xsr = XMLInputFactory.newFactory().createXMLStreamReader(br);
            xsr.nextTag();
            String nsUri = xsr.getNamespaceURI();
            try (BufferedReader br2 = reset(readerSupplier, br)) {

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.EnumSet;
import java.util.List;
import java.util.stream.Stream;