def METHOD_NAME(filename, old_string, new_string) -> bool:
    # Safely read the input filename using 'with'
    with open(filename) as f:
        s = f.read()
        if old_string not in s:
            #print('"{old_string}" not found in {filename}.'.format(**locals()))
            return False
    # Safely write the changed content, if found in the file
    with open(filename, 'w') as f:
        #print('Changing "{old_string}" to "{new_string}" in {filename}'.format(**locals()))
        s = s.replace(old_string, new_string)
        f.write(s)
        return True