code: def importTTX(self):
          
          import os
          import re
  
          prefix = "com.github.fonttools.ttx"
          sfntVersionRE = re.compile('(^<ttFont\s+)(sfntVersion=".*"\s+)(.*>$)',
                                     flags=re.MULTILINE)
          if not hasattr(self.ufo, "data"):
              return
          if not self.ufo.data.fileNames:
              return
          for path in self.ufo.data.fileNames:
              foldername, filename = os.path.split(path)
              if (foldername == prefix and filename.endswith(".ttx")):
                  ttx = self.ufo.data[path].decode('utf-8')
                  # strip 'sfntVersion' attribute from ttFont element,
                  # if present, to avoid overwriting the current value
                  ttx = sfntVersionRE.sub(r'\1\3', ttx)
                  fp = BytesIO(ttx.encode('utf-8'))
                  self.otf.importXML(fp)
docs: Merge TTX files from data directory "com.github.fonttools.ttx"
  
          **This should not be called externally.** Subclasses
          may override this method to handle the bounds creation
          in a different way if desired.