Extends does not work if right hand side of connection is not present

[GillisWerrebrouck]

Extends is not present if the right hand side of a connection is not present.

Example:

class A {
        + someProp string
        - someOtherProp number

        + number computeSomething(string x)
    }
A --|> B
@enduml```

Code:
```class A {
  private string : someProp;
  private number : someOtherProp;
  computeSomething(x) {
    return;
  }
}```

Expected:
```class A extends B {
  private string : someProp;
  private number : someOtherProp;
  computeSomething(x) {
    return;
  }
}```