docstr: xml-escape the given unicode string. 
docstr_tok: ["xml-escape","the","given","unicode","string","."]
code: def __call__(self, ustring):
      """xml-escape the given unicode string."""
      try:
          ustring = unicode(ustring)
      except UnicodeDecodeError:
          ustring = unicode(ustring, "utf-8", errors="replace")
      return self.charef_rex.sub(self._replacer, ustring)
  
imports: import sys, re
label_desc: Use image node_id 3 for calling the _escape obj's underlying member method code with example usage: obj.__call__(ustring) and returns: self