What should the `next` method contain to implement iteration?

The next method (or __next__ in Python 3) should:

1. Return the next item in the iteration.
2. Raise a StopIteration exception when there are no more items.

// Example implementation of the __next__ method for a simple iterator
class MyIterator:
    def __init__(self, data):
        self.data = data
        self.index = 0

    def __iter__(self):
        return self

    def __next__(self):
        if self.index >= len(self.data):
            raise StopIteration  // Exception at the end of iteration
        value = self.data[self.index]
        self.index += 1
        return value  // Return the next element