code: @CanIgnoreReturnValue
    public MapMaker initialCapacity(int initialCapacity) {
      checkState(
          this.initialCapacity == UNSET_INT,
          "initial capacity was already set to %s",
          this.initialCapacity);
      checkArgument(initialCapacity >= 0);
      this.initialCapacity = initialCapacity;
      return this;
    }
docs: Sets the minimum total size for the internal hash tables. For example, if the initial capacity
  is {@code 60}, and the concurrency level is {@code 8}, then eight segments are created, each
  having a hash table of size eight. Providing a large enough estimate at construction time
  avoids the need for expensive resizing operations later, but setting this value unnecessarily
  high wastes memory.
  
  @throws IllegalArgumentException if {@code initialCapacity} is negative
  @throws IllegalStateException if an initial capacity was already set