**English**

From a set of ints you have to create a list of closed intervals as tuples, so the intervals are covering all the values found in the set.

In this mission you should use the 'yield' to make your function a generator.

A closed interval includes its endpoints! The interval *1..5*, for example,
includes each value *x* that satifies the condition
*1 <= x <= 5*.

Values can only be in the same interval if the difference between a value and the next
smaller value in the set equals one, otherwise a new interval begins. Of course, the
start value of an interval is excluded from this rule.

A single value, that does not fit into an existing interval becomes the start- and
endpoint of a new interval.

**Input:**A set of ints.

**Output:**A list of tuples of two ints, indicating the endpoints of the interval. The list should be sorted by start point of each interval.

**Examples:**

create_intervals({1, 2, 3, 4, 5, 7, 8, 12}) == [(1, 5), (7, 8), (12, 12)] create_intervals({1, 2, 3, 6, 7, 8, 4, 5}) == [(1, 8)]