def nil_instance_vars(object, vars)
    vars = Array(vars)
    vars.select { |var| object.instance_variable_get(var).nil? }
  end
def nil_instance_vars(object, vars)
    vars = Array(vars)
    vars.select { |var| object.instance_variable_get(var).nil? }
  end
Returns an array containing each symbol in vars for which the
 corresponding instance variable  in the specified object is nil.