code: def get_engine_spec(
      backend: str, driver: Optional[str] = None
  ) -> type[BaseEngineSpec]:
      """
      Return the DB engine spec associated with a given SQLAlchemy URL.
  
      Note that if a driver is not specified the function returns the first DB engine spec
      that supports the backend. Also, if a driver is specified but no DB engine explicitly
      supporting that driver exists then a backend-only match is done, in order to allow new
      drivers to work with Superset even if they are not listed in the DB engine spec
      drivers.
      """
      engine_specs = load_engine_specs()
  
      if driver is not None:
          for engine_spec in engine_specs:
              if engine_spec.supports_backend(backend, driver):
                  return engine_spec
  
      # check ignoring the driver, in order to support new drivers; this will return a
      # random DB engine spec that supports the engine
      for engine_spec in engine_specs:
          if engine_spec.supports_backend(backend):
              return engine_spec
  
      # default to the generic DB engine spec
      return BaseEngineSpec
  
file_path: superset/superset/db_engine_specs/__init__.py
imports: import inspect
  import logging
  import pkgutil
  from collections import defaultdict
  from importlib import import_module
  from pathlib import Path
  from typing import Any, Optional
  import sqlalchemy.dialects
  from importlib_metadata import entry_points
  from sqlalchemy.engine.default import DefaultDialect
  from sqlalchemy.exc import NoSuchModuleError
  from superset import app, feature_flag_manager
  from superset.db_engine_specs.base import BaseEngineSpec
label_desc: Use image node_id 3 for calling a global function with example usage: get_engine_spec(backend, driver) and returns: BaseEngineSpec, engine_spec, engine_spec