why it showed that the argument of my function was not defined?

[Tony]

here is my codes,I wrote a function which should be able to read a csv file and parse it into some useful form.

import csv


def load_atlas(filename):
    edited_file = []
    with open('filename', 'r') as csv_file:
        csv_reader = csv.reader(csv_file, delimiter='|')
        for lines in csv_reader:
            edited_file.append(lines)
    return edited_file
load_atlas(ala-acton.txt)

my problem is whenever i passed a filename into this function, it returns an error

Error:
NameError: name 'ala' is not defined