docstr: Update a configuration dictionary
  that can set the correct properties for impersonating users
  :param connect_args: config to be updated
  :param uri: URI string
  :param username: Effective username
  :return: None
docstr_tok: ["Update","a","configuration","dictionary","that","can","set","the","correct","properties","for","impersonating","users",":","param","connect_args",":","config","to","be","updated",":","param","uri",":","URI","string",":","param","username",":","Effective","username",":","return",":","None"]
code: def update_impersonation_config(
      cls,
      connect_args: dict[str, Any],
      uri: str,
      username: str | None,
  ) -> None:
      """
      Update a configuration dictionary
      that can set the correct properties for impersonating users
      :param connect_args: config to be updated
      :param uri: URI string
      :param username: Effective username
      :return: None
      """
      url = make_url_safe(uri)
      backend_name = url.get_backend_name()
  
      # Must be Trino connection, enable impersonation, and set optional param
      # auth=LDAP|KERBEROS
      # Set principal_username=$effective_username
      if backend_name == "trino" and username is not None:
          connect_args["user"] = username
  
imports: from __future__ import annotations
  import contextlib
  import logging
  import threading
  import time
  from typing import Any, TYPE_CHECKING
  import simplejson
  from flask import current_app
  from sqlalchemy.engine.reflection import Inspector
  from sqlalchemy.engine.url import URL
  from sqlalchemy.exc import NoSuchTableError
  from superset import db
  from superset.constants import QUERY_CANCEL_KEY, QUERY_EARLY_CANCEL_KEY, USER_AGENT
  from superset.databases.utils import make_url_safe
  from superset.db_engine_specs.base import BaseEngineSpec
  from superset.db_engine_specs.exceptions import SupersetDBAPIConnectionError
  from superset.db_engine_specs.presto import PrestoBaseEngineSpec
  from superset.models.sql_lab import Query
  from superset.superset_typing import ResultSetColumnType
  from superset.utils import core
label_desc: Use image node_id 2 for calling the TrinoEngineSpec obj's underlying member method code with example usage: obj.update_impersonation_config(cls, connect_args, uri, username) without return types