code: function (value, defaultValue) {
        var count = React.Children.count(this.props.children);
        switch (count) {
          case 0:
            return value.length > 0 ? value : defaultValue;
          case value.length:
            return value;
          case defaultValue.length:
            return defaultValue;
          default:
            if (value.length !== count || defaultValue.length !== count) {
              console.warn(this.constructor.displayName + ": Number of values does not match number of children.");
            }
            return linspace(this.props.min, this.props.max, count);
        }
      }
docs: Check if the arity of `value` or `defaultValue` matches the number of children (= number of custom handles). If no custom handles are provided, just returns `value` if present and `defaultValue` otherwise. If custom handles are present but neither `value` nor `defaultValue` are applicable the handles are spread out equally. TODO: better name? better solution?