"""
   Takes a string as input and counts how many lowercase 'a' characters this string contains.
   Note that uppercase 'A' does not count.
   Example: count_a("banana") returns 3 
            -> because lowercase 'a' appears 3 times
"""
def count_a(text):
    count = 0
    for char in text:
        if char == 'a':
            count += 1
    return count