code: def defaultMakeInstanceFilename(
      doc: DesignSpaceDocument,
      instance: InstanceDescriptor,
      statNames: StatNames,
  ) -> str:
      """Default callable to synthesize an instance filename
      when makeNames=True, for instances that don't specify an instance name
      in the designspace. This part of the name generation can be overriden
      because it's not specified by the STAT table.
      """
      familyName = instance.familyName or statNames.familyNames.get(
          "en"
      )
      styleName = instance.styleName or statNames.styleNames.get("en")
      return f"{familyName}-{styleName}.ttf"
  
file_path: catboost/contrib/python/fonttools/fontTools/designspaceLib/split.py
imports: from __future__ import annotations
  import itertools
  import logging
  import math
  from typing import Any, Callable, Dict, Iterator, List, Tuple, cast
  from fontTools.designspaceLib import AxisDescriptor, AxisMappingDescriptor, DesignSpaceDocument, DiscreteAxisDescriptor, InstanceDescriptor, RuleDescriptor, SimpleLocationDict, SourceDescriptor, VariableFontDescriptor
  from fontTools.designspaceLib.statNames import StatNames, getStatNames
  from fontTools.designspaceLib.types import ConditionSet, Range, Region, getVFUserRegion, locationInRegion, regionInRegion, userRegionToDesignRegion
label_desc: Use image node_id 1 for calling a global function with example usage: defaultMakeInstanceFilename(doc, instance, statNames) and returns: familyName, str, styleName, str