code: @Override
      public ChronicleMapBuilder<K, V> constantKeySizeBySample(K sampleKey) {
          this.sampleKey = sampleKey;
          averageKey = null;
          averageKeySize = UNDEFINED_DOUBLE_CONFIG;
          return this;
      }
docs: {@inheritDoc}
  <p>
  <p>For example, if your keys are Git commit hashes:<pre>{@code
  Map<byte[], String> gitCommitMessagesByHash =
  ChronicleMapBuilder.of(byte[].class, String.class)
  .constantKeySizeBySample(new byte[20])
  .create();}</pre>
  
  @see #averageKeySize(double)
  @see #averageKey(Object)
  @see #constantValueSizeBySample(Object)