code: def toXML(self, writer, ttFont):
      for axis in self.axes:
          axis.toXML(writer, ttFont)
      for instance in self.instances:
          instance.toXML(writer, ttFont)
  
imports: from fontTools.misc import sstruct
  from fontTools.misc.fixedTools import fixedToFloat, floatToFixed, floatToFixedToStr, strToFixedToFloat
  from fontTools.misc.textTools import Tag, bytesjoin, safeEval
  from fontTools.ttLib import TTLibError
  from .None import DefaultTable
  import struct
label_desc: Use image node_id 4 for calling the table__f_v_a_r obj's underlying member method code with example usage: obj.toXML(writer, ttFont) without return types