Function _singleOrDefault

_singleOrDefault<T>(src: Iterable<T>, pred?: IndexedPredicate<T>): T | undefined
Returns the unique element that satisfies the optional predicate, or undefined when no match is found.
Type Parameters
- T
  Element type produced by the source iterable.
Parameters
- src: Iterable<T>
  Source iterable to evaluate.
- pred: IndexedPredicate<T> = ...
  Predicate receiving each element and its index; the matching element must be unique when provided.
Returns T | undefined
The sole element accepted by pred, or undefined when no element matches.
Throws
Error Thrown when more than one element satisfies pred.

Throws
Error Rethrows any error thrown by pred.
Example
```
const value = _singleOrDefault([1, 2, 3], (item) => item > 3);
console.log(value); // undefined
```
or using the curried version:
```
const value = pipeInto(
  [1, 2, 3],
  singleOrDefault((item) => item > 3)
);
console.log(value); // undefined
```
- Defined in src/transformers/singleOrDefault.ts:29