For the exercises in Part A$,$ your solutions can use:

a for loop to iterate over the characters in a string.

the string concatenation operator $($e$.$g$.,$ s$1+$ s$2).$

the string replication operator $($e$.$g$.,s**n$ or $n**s.$

Python's built$-$in len, min and max functions.

Your solutions cannot use:

the in and not in operators $($e$.$g$.,$ if s$1$ in s$2$:$...)$;

slicing $($e$.$g$.,$ slice $=$ s$[$i : j$])$;

any of the methods provided by type str; for example, count, find, index, join, replace, rfind, rindex and many more.Exercise $3$

Use the function design recipe to develop a function named has$\_$pair. The function header $($with missing type annotations$)$ is: has$\_$pair $(s,ch).$ Parameter $s$ is a string that has at least two characters. Parameter ch is a string containing exactly one character. The function returns True if $s$ contains two occurrences of ch next to each other; otherwise it returns False.

For example, when has$\_$pair is called this way: has$\_$pair$(\text{'}$abccd$\text{'},\text{'}c\text{'}),$ the function returns True, because 'abccd' contains a $\text{'}c\text{'}$ next to a $\text{'}c\text{'}.$ When has$\_$pair is called this way: has$\_$pair$(\text{'}$abcdc$\text{'},\text{'}$c$\text{'}),$ the function returns False. Although 'abcdc' contains two occurrences of $\text{'}c\text{'},$ the first one isn't beside the second one.

Your function must have exactly one loop.

Your function definition must have type annotations and a complete docstring. Use the Python shell to test has$\_$pair.