code: def mergeLangSyses(lst):
      assert lst
  
      # TODO Support merging ReqFeatureIndex
      assert all(l.ReqFeatureIndex == 0xFFFF for l in lst)
  
      self = otTables.LangSys()
      self.LookupOrder = None
      self.ReqFeatureIndex = 0xFFFF
      self.FeatureIndex = mergeFeatureLists(
          [l.FeatureIndex for l in lst if l.FeatureIndex]
      )
      self.FeatureCount = len(self.FeatureIndex)
      return self
  
imports: from fontTools import ttLib
  from fontTools.ttLib.tables.DefaultTable import DefaultTable
  from fontTools.ttLib.tables import otTables
  from fontTools.merge.base import add_method, mergeObjects
  from fontTools.merge.util import *
  import logging
label_desc: Use image node_id 4 for calling a global function with example usage: mergeLangSyses(lst) and returns: self