def processingInstruction(self, target, data):
        # NOTE this seems to never be called by the parser.
        mo = XML_HEADER_RE.match(data)
        if mo:
            version, encoding = mo.groups()
            assert version == "1.0"
            self.encoding = encoding
            if self.doc:
                self.doc.set_encoding(encoding)
        else:
            self._errormethod("!!! Unhandled pi: %r" % (data,))
handle: xml version="1.0" encoding="ISO-8859-1"?
dataset/ETHPy150Open kdart/pycopia/XML/pycopia/XML/POMparse.py/ContentHandler.processingInstruction