android/guava/src/com/google/common/collect/Maps.java
static <K, V> boolean containsEntryImpl(Collection<Entry<K, V>> c, Object o) {
    if (!(o instanceof Entry)) {
      return false;
    }
    return c.contains(unmodifiableEntry((Entry<?, ?>) o));
  }
static <K, V> boolean containsEntryImpl(Collection<Entry<K, V>> c, Object o) {
    if (!(o instanceof Entry)) {
      return false;
    }
    return c.contains(unmodifiableEntry((Entry<?, ?>) o));
  }
Implements {@code Collection.contains} safely for forwarding collections of map entries. If
{@code o} is an instance of {@code Entry}, it is wrapped using {@link #unmodifiableEntry} to
protect against a possible nefarious equals method.

<p>Note that {@code c} is the backing (delegate) collection, rather than the forwarding
collection.

@param c the delegate (unwrapped) collection of map entries
@param o the object that might be contained in {@code c}
@return {@code true} if {@code c} contains {@code o}