code: @SuppressWarnings("unchecked")
      public K boost(Number boost) {
          this.boost = boost == null ? null : boost.floatValue();
          return (K) this;
      }
docs: Sets the boost for the {@link Condition} to be built. Documents matching this condition will (in addition to the
  normal weightings) have their score multiplied by {@code boost}. If {@code null}, then {@link
  Condition#DEFAULT_BOOST}
  
  @param boost The boost for the {@link Condition} to be built.
  @return This builder with the specified boost.