## Objective

Create a function to perform the NOT binary operation on a binary string.

Very easy

## Description

Computers, as we all know, operate on binary numbers — numbers whose every single digit is either a 0 or a 1; hence the name 'binary'.

From the circuitry of the processor, to the input and output from I/O devices, to the wireless signals transmitted back and forth to the involved machinery, everything in the world of computers works on these magical numbers.

Typically numerous operations are performed on binary numbers. Amongst the most common is the NOT operation, sometimes comprehensively referred to as the bitwise NOT, or the bitwise complement operation.

The operation proceeds as follows: each bit in the binary number is inverted. That is, if it is 0, it's made 1; and similarly if it's 1, it's made 0.

In this exercise, you ought to create a function `not()` that takes as input a binary number in the form of a string (such as `'10100'`) and then returns back its value after performing the bitwise NOT operation on it, once again in the form of a string.

If an empty string is given, the function should return back `''` as well.

Below shown are some examples of the usage of this function:

``not('1010')``
'0101'
``not('1111')``
'0000'
``not('0000')``
'1111'
``not('00001')``
'11110'
``not('1')``
'0'
``not('')``
''