My output from NSolve is a list of rules, most of these are undefined, I want to remove those rules.
More specifically I have a list

```
    rules = {y2 -> Undefined, y3 -> Undefined, y4 -> Undefined, y5 -> Undefined, 
 y6 -> Undefined, y7 -> Undefined, y8 -> Undefined, y9 -> Undefined, 
 y10 -> Undefined, y11 -> Undefined, \[Lambda]2 -> -1.68379, 
 y2 -> 0.991506, y3 -> Undefined, y4 -> Undefined, y5 -> Undefined, 
 y6 -> Undefined, y7 -> Undefined, y8 -> Undefined, y9 -> Undefined, 
 y10 -> Undefined, y11 -> 0.991506, \[Lambda]2 -> Undefined, 
 y2 -> Undefined, y3 -> 0.97847, y4 -> 0.969246, y5 -> 0.963328, 
 y6 -> 0.96037, y7 -> 0.96037, y8 -> 0.963328, y9 -> 0.969246, 
 y10 -> 0.97847, y11 -> Undefined, \[Lambda]2 -> Undefined}

```

and I want to get

```
{y2-> 0.991506, y3-> 0.969246,y4 -> 0.969246...}

```

and so on.
How do I remove all the undefined defitions, not that the final list doesnt have to be in this order.
`DeleteCases` and other functions didn't help.