function coerceToString(value) {
    var defaultValue = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : '';

    if (isNil(value)) {
      return defaultValue;
    }

    if (isString(value)) {
      return value;
    }

    return String(value);
  }
Get the string representation of the `value`.
Converts the `value` to string.
If `value` is `null` or `undefined`, return `defaultValue`.

@ignore
@function toString
@param {*} value             The value to convert.
@param {*} [defaultValue=''] The default value to return.
@return {string|null}        Returns the string representation of `value`. Returns `defaultValue` if `value` is
                             `null` or `undefined`.