if (context == null) {
            return null;
        }
        return context.get(key);
    }

    /**
     * Sets the project's class realm. <strong>Warning:</strong> This is an internal utility method that is only public
     * for technical reasons, it is not part of the public API. In particular, this method can be changed or deleted
     * without prior notice and must not be used by plugins.
     *

    return None.INSTANCE;
  }

  /**
   * Determines whether a character is whitespace according to the latest Unicode standard, as
   * illustrated <a
   * href="http://unicode.org/cldr/utility/list-unicodeset.jsp?a=%5Cp%7Bwhitespace%7D">here</a>.
   * This is not the same definition used by other Java APIs. (See a <a
   * href="https://goo.gl/Y6SLWx">comparison of several definitions of "whitespace"</a>.)
   *

    return None.INSTANCE;
  }

  /**
   * Determines whether a character is whitespace according to the latest Unicode standard, as
   * illustrated <a
   * href="http://unicode.org/cldr/utility/list-unicodeset.jsp?a=%5Cp%7Bwhitespace%7D">here</a>.
   * This is not the same definition used by other Java APIs. (See a <a
   * href="https://goo.gl/Y6SLWx">comparison of several definitions of "whitespace"</a>.)
   *

    return ImmutableSet.copyOf(elements);
  }

  private static <E> List<E> list(E... elements) {
    return ImmutableList.copyOf(elements);
  }

  /**
   * Utility method to verify that the given LinkedHashSet is equal to and hashes identically to a
   * set constructed with the elements in the given collection. Also verifies that the ordering in

 *
 * <p>Note to Guice users: {@code TypeToken} is similar to Guice's {@code TypeLiteral} class except
 * that it is serializable and offers numerous additional utility methods.
 *
 * @author Bob Lee
 * @author Sven Mawson
 * @author Ben Yu
 * @since 12.0
 */
@SuppressWarnings("serial") // SimpleTypeToken is the serialized form.
@ElementTypesAreNonnullByDefault

import java.util.Queue;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * This class contains static utility methods that operate on or return objects of type {@link
 * Iterator}. Except as noted, each method has a corresponding {@link Iterable}-based method in the
 * {@link Iterables} class.
 *

import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to the {@link Future} interface.
 *
 * <p>Many of these methods use the {@link ListenableFuture} API; consult the Guava User Guide

import java.util.Queue;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * This class contains static utility methods that operate on or return objects of type {@link
 * Iterator}. Except as noted, each method has a corresponding {@link Iterable}-based method in the
 * {@link Iterables} class.
 *

import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to {@link Set} instances. Also see this class's counterparts
 * {@link Lists}, {@link Maps} and {@link Queues}.
 *
 * <p>See the Guava User Guide article on <a href=

    ASSERT_NE(*op, nullptr);
  }

  FunctionDef fdef() {
    tensorflow::FunctionDef fdef;
    EXPECT_TRUE(GetFunctionDef(func_, &fdef));
    return fdef;
  }

  // logging utility
  template <class Container>
  string ToString(const Container& v) {
    std::stringstream ss;
    ss << "{";
    size_t i = 0;
    for (const auto& e : v) {
      if (i != 0) {
        ss << ", ";