Implement null references metrics

[doritosxxx]

#10

[yegor256]

@rultor merge

[rultor]

@rultor merge

@yegor256 OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor merge

@doritosxxx @yegor256 Oops, I failed. You can see the full log here (spent 8min)

+ java -jar /opt/app/jpeek-0.32.0-jar-with-dependencies.jar --help
Usage: <main class> [options]
  Options:
    --help
      Print usage options
    --include-ctors
      Include constructors into all formulas
      Default: false
    --include-private-methods
      Include private methods into all formulas
      Default: false
    --include-static-methods
      Include static methods into all formulas
      Default: false
    --metrics
      Comma-separated list of metrics to include
      Default: LCOM5,NHD,MMAC,SCOM,CAMC
    --overwrite
      Overwrite the target directory if it exists (otherwise an error is 
      raised) 
      Default: false
    --quiet
      Turn logging off
      Default: false
  * --sources, -s
      Directory with .class files
  * --target, -t
      Output directory

+ locale
LANG=en_US.UTF-8
LANGUAGE=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=en_US.UTF-8
++ dirname dataset/temp/env-done.txt
+ mkdir -p dataset/temp
+ date +%s%N
Finished, in 4s
+ make lint



+++ lint +++

\u001b[1m/home/r/repo/metrics/ast.py\u001b[m\u001b[36m:\u001b[m148\u001b[36m:\u001b[m1\u001b[36m:\u001b[m \u001b[1m\u001b[31mE302\u001b[m expected 2 blank lines, found 1
\u001b[1m/home/r/repo/metrics/ast.py\u001b[m\u001b[36m:\u001b[m158\u001b[36m:\u001b[m1\u001b[36m:\u001b[m \u001b[1m\u001b[31mE302\u001b[m expected 2 blank lines, found 1
make: *** [Makefile:85: lint] Error 1
container df6f9299a084984f0922b6c5125030a5d92bffd18c2a056b8fd7e1c167c73711 is dead
Fri Oct 27 11:06:53 AM CEST 2023

[yegor256]

@doritosxxx the formatting of your Python code is not pefect. Try make clean lint to see this error on your laptop

[yegor256]

@doritosxxx I reimplemented your code in 3ebc461, thanks for your contribution!