def count$\_$letters$($text$)$:

# Initialize a new dictionary.

dictionary $=\_\_\_$

# Complete the for loop to iterate through each "text" character and

# use a string method to ensure all letters are lowercase.

for $\_\_\_$

# Complete the if$-$statement using a string method to check if the

# character is a letter.

if$\_\_\_$

# Complete the if$-$statement using a logical operator to check if

# the letter is not already in the dictionary.

if $\_\_\_$

# Use a dictionary operation to add the letter as a key

# and set the initial count value to zero.

$\_\_\_$

# Use a dictionary operation to increment the letter count value

# for the existing key.

$\_\_\_$

$\_\_\_$ # Increment the letter counter.

return dictionary

print$($count$\_$letters$("$AaBbCc$"))$

# Should be $\{\text{'}$a$\text{'}$: $2,\text{'}$b$\text{'}$: $2,\text{'}$c$\text{'}$: $2\}$

print$($count$\_$letters$("$Math is fun! $2+2=4"))$

# Should be $\{\text{'}$m$\text{'}$: $1,\text{'}$a$\text{'}$: $1,\text{'}$t$\text{'}$: $1,\text{'}$h$\text{'}$: $1,\text{'}$i$\text{'}$: $1,\text{'}$s$\text{'}$: $1,\text{'}$f$\text{'}$: $1,\text{'}$u$\text{'}$: $1,\text{'}$n$\text{'}$: $1\}$

print$($count$\_$letters$("$This is a sentence."$))$

# Should be $\{\text{'}$t$\text{'}$: $2,\text{'}$h$\text{'}$: $1,\text{'}$i$\text{'}$: $2,\text{'}$s$\text{'}$: $3,\text{'}$a$\text{'}$: $1,\text{'}$e$\text{'}$: $3,\text{'}$n$\text{'}$: $2,\text{'}$c$\text{'}$: $1\}$