code: def startPrefixMapping(self, prefix, uri):
      self._ns_contexts.append(self._current_context.copy())
      self._current_context[uri] = prefix
      self._undeclared_ns_maps.append((prefix, uri))
  
imports: import os, urllib.parse, urllib.request
  import io
  import codecs
  from .None import handler
  from .None import xmlreader
label_desc: Use image node_id 6 for calling the XMLGenerator obj's underlying member method code with example usage: obj.startPrefixMapping(prefix, uri) without return types