isValid(value = "") {
      if (value === "") {
        return true;
      }
      return !!this.getFormat().parse(value);
    }
Checks if a value is valid against the current date format of the DatePicker.
@public
@method
@name sap.ui.webc.main.DatePicker#isValid
@param { string } [value=""] A value to be tested against the current date format
@returns { boolean }