standardize strings with .format()

In file: __init__.py, request.py and helpers.py : string with %s can be replaced by .format() function, prevents bug "UnicodeDecodeError: 'ascii' codec can't decode byte 0xd1 in position 2: ordinal not in range(128)"

In file: helpers.py: functions: filter, map, reduce can be replaced by compressing list becomes more legible.