docstr: Gets the RUSAGE memory usage, returns in K. Encapsulates the difference
  between macOS and Linux rss reporting
  
  :returns: memory usage in kilobytes
code: def _get_mem_usage(self):
      """
      Gets the RUSAGE memory usage, returns in K. Encapsulates the difference
      between macOS and Linux rss reporting
  
      :returns: memory usage in kilobytes
      """
  
      from resource import RUSAGE_SELF, getrusage
  
      mem = getrusage(RUSAGE_SELF).ru_maxrss
      if sys.platform == "darwin":
          # man 2 getrusage:
          #     ru_maxrss
          # This is the maximum resident set size utilized (in bytes).
          return mem / 1024  # Kb
      else:
          # linux
          # man 2 getrusage
          #        ru_maxrss (since Linux 2.6.32)
          #  This is the maximum resident set size used (in kilobytes).
          return mem
  
imports: import logging
  import os
  import shutil
  import sys
  import sysconfig
  import tempfile
  from io import BytesIO
  import pytest
  from packaging.version import parse
  from PIL import Image, ImageMath, features
label_desc: Use image node_id 1 for calling the PillowLeakTestCase obj's underlying member method code with example usage: obj._get_mem_usage() and returns: unknown, mem