class_docstr: Simple, type-checked, dict-like container for with submessage values.
class_docstr_tok: ["Simple",",","type-checked",",","dict-like","container","for","with","submessage","values","."]
code: def __getitem__(self, key):
      try:
          return self._values[key]
      except KeyError:
          key = self._key_checker.CheckValue(key)
          new_element = self._message_descriptor._concrete_class()
          new_element._SetListener(self._message_listener)
          self._values[key] = new_element
          self._message_listener.Modified()
  
          return new_element
  
imports: import collections
  import sys
label_desc: Use image node_id 2 for calling the MessageMap obj's underlying member method code with example usage: obj.__getitem__(key) and returns: self, new_element