def __get_vm_attr_variable_value(var_config_values, vm_dict):
    """
    Returns the associated value contained on a VM instance
    :param var_config_values: the configuration dictionary
    :param vm_dict: the dictionary containing all VMs where the key is the VM's
                    name
    :return: the value
    """
    vm = vm_dict.get(var_config_values['vm_name'])
    if vm:
        if var_config_values['value'] == 'floating_ip':
            return vm.get_floating_ip().ip
        if var_config_values['value'] == 'image_user':
            return vm.get_image_user()