Source Code Byte Frequency Source Code Byte Frequency

Write a program that get a single byte character as an input and prints the frequency of that byte in the program's source code as an output.
Examples:
Assuming my program is: ab#cd%b then the output of the program should be (each line is a separate execution):
input         output
-----         ------
  a           0.1428571428571429
  b           28.57%
  #           14.2857143%
  c           1/7
  B           0


Rules:

The format of the proportion does not need to be consistent across all inputs, e.g. a fraction for one, decimal for another, percent for a third, plain zero for non-existent byte, etc...
If a proportion is represented as decimal, the result must be accurate to at least 4 decimal places.
Source code should be at least 1 byte long.


Scoring:
This is code-golf - the shortest code (≥1) wins.

(It would also be fun to get the shortest code in every language, so don't hesitate to post multiple entries)
JavaScript (ES6), 40 bytes
All used characters appear exactly twice. Therefore, this returns either 0 or 2/40 = 0.05.

F=_=&gt;(F+'+./02&gt;cdeilnsu').includes(_)/20

Try it online!