class_docstr: A logging filter designed to record missing reference warning messages
  for use by this extension
code: def filter(self, record):
      self._record_reference(record)
      return True
  
imports: from collections import defaultdict
  import json
  import logging
  from pathlib import Path
  from docutils.utils import get_source_line
  from docutils import nodes
  from sphinx.util import logging
  import matplotlib
label_desc: Use image node_id 3 for calling the MissingReferenceFilter obj's underlying member method code with example usage: obj.filter(record) and returns: True