Unify generics code

**Is your feature request related to a problem? Please describe.**
The code for iterating over sequences and collections is scattered across multiple classes due to the fact that golang has no support for generics.

**Describe the solution you'd like**
Write a generic iterator code once and then wrappers to perform appropriate type coercion . Possible candidates are:

- [ ] `Iterator` and derived types
- [ ] `FiniteIterator` and derived types

**Describe alternatives you have considered**
[Golang does not support generics](https://appliedgo.net/generics/) .