code: def _anchorDefinition(self, anchordef):
      anchorname = anchordef.name
      glyphname = anchordef.glyph_name
      anchor = self._anchor(anchordef.pos)
  
      if anchorname.startswith("MARK_"):
          name = "_".join(anchorname.split("_")[1:])
          markclass = ast.MarkClass(self._className(name))
          glyph = self._glyphName(glyphname)
          markdef = MarkClassDefinition(markclass, anchor, glyph)
          self._markclasses[(glyphname, anchorname)] = markdef
      else:
          if glyphname not in self._anchors:
              self._anchors[glyphname] = {}
          if anchorname not in self._anchors[glyphname]:
              self._anchors[glyphname][anchorname] = {}
          self._anchors[glyphname][anchorname][
              anchordef.component
          ] = anchor
  
imports: import logging
  import re
  from io import StringIO
  from fontTools.feaLib import ast
  from fontTools.ttLib import TTFont, TTLibError
  from fontTools.voltLib import ast
  from fontTools.voltLib.parser import Parser
label_desc: Use image node_id 18 for calling the VoltToFea obj's underlying member method code with example usage: obj._anchorDefinition(anchordef) without return types