Write a function calculate_file_size that consumes the name of a file as a string and returns an integer indicating how many characters long the file’s contents is using the Count pattern (you may not use the built-in len function). Call your function on the files below to unit test. The rainfall file has 891 characters, the names file has 1064 characters, and the empty file has 0 characters.

The files are in rainfall.txt, names.txt and empty.txt, and in the rainfall.txt, names.txt and empty.txt tabs of the sandbox (To sandbox).

The first lines of rainfall.txt:

0
0
0
0
0
0
0.5
0
...

The first lines of names.txt:

gatsby,jay
caulfield,holden
humbert,humbert
bloom,leopold
angstrom,rabbit
...