#Write a function called lucky$\_$sevens that takes in one

#parameter, a string variable named a$\_$string. Your function

#should return True if there are exactly three $\text{'}7\text{'}$s in

#a$\_$string. If there are less than three or more than three

#$\text{'}7\text{'}$s$,$ the function should return False.

#

#For example:

# $-$ lucky$\_$sevens$("$happy$777$bday"$)$ should return True.

# $-$ lucky$\_$sevens$("$h$7$app$7$ybd$7$ay$")$ should also return True.

# $-$ lucky$\_$sevens$("$happy$77$bday"$)$ should return False.

# $-$ lucky$\_$sevens$("$h$777$appy$777$bday"$)$ should also return False.

#

#Hint: Remember in Chapter $3\mathrm{.}3,$ we covered how to use a loop

#to look at each character in a string.

#Write your function here!

#Below are some lines of code that will test your function.

#You can change the value of the variable$($s$)$ to test your

#function with different inputs.

#

#If your function works correctly, this will originally

#print: True, True, False, False, each on their own line.