'Validate this link, currently only checking whether it has
a value when required=True
@param form: the form'

def validate(self, form):

    required = self.options.required
    if (not required):
        return
    fname = self._formname(separator='_')
    values = form.vars.get(fname)
    if (not values):
        error = (current.T('Value    Required') if (required is True) else required)
        form.errors[fname] = error
