code: def get_sql_engine(
      url: Optional[str] = None,
      strict=False,
      echo: bool = False,
  ) -> Engine:
      """gets a sqlalchemy Engine instance
  
      Args:
      url: url of database, if None, uses DB_URL_ENV environment variable or
           SQLITE_FILE_DB_URL as fallbacks, in that order
      strict: if True, won't attempt to fall back to local or memory engines.
      echo: if True, will echo all SQL commands to terminal
  
      Returns:
      sqlalchemy Engine instance
      """
      if url is None:
          url = os.environ.get(DB_URL_ENV) or SQLITE_FILE_DB_URL
  
      try:
          return _create_sqa_engine(url=url, echo=echo)
  
      except (OperationalError, OSError) as e:
          logging.error("")
          logging.error(
              t.red(
                  f"Caliban failed to connect to its experiment tracking database! Details:"
              )
          )
          logging.error("")
          logging.error(t.red(str(e)))
          logging.error(
              t.red(f"Caliban attempted to connect to '{url}'.")
          )
          logging.error(
              t.red(f"Try setting a different URL using ${DB_URL_ENV}.")
          )
          logging.error("")
  
          if strict:
              sys.exit(1)
  
          else:
              # For now, we allow two levels of fallback. The goal is to make sure that
              # the job can proceed, no matter what.
              #
              # If you specify a custom URL, Caliban will fall back to the local
              # default database location. If that fails, Caliban will attempt once
              # more using an in-memory instance of SQLite. The only reason that should
              # fail is if your system doesn't support SQLite at all.
  
              if url == SQLITE_FILE_DB_URL:
                  logging.warning(
                      t.yellow(
                          f"Attempting to proceed with in-memory database."
                      )
                  )
  
                  # TODO when we add our strict flag, bail here and don't even allow
                  # in-memory.
                  logging.warning(
                      t.yellow(
                          f"WARNING! This means that your job's history won't be accessible "
                          f"via any of the `caliban history` commands. Proceed at your future self's peril."
                      )
                  )
                  return get_sql_engine(
                      url=MEMORY_DB_URL, strict=True, echo=echo
                  )
  
              logging.info(
                  t.yellow(
                      f"Falling back to local sqlite db: {SQLITE_FILE_DB_URL}"
                  )
              )
              return get_sql_engine(
                  url=SQLITE_FILE_DB_URL, strict=False, echo=echo
              )
  
imports: import os
  import sys
  from contextlib import contextmanager
  from copy import deepcopy
  from typing import Any, Dict, List, Optional
  from absl import logging
  from blessings import Terminal
  from googleapiclient import discovery
  from sqlalchemy import create_engine
  from sqlalchemy.engine.base import Engine
  from sqlalchemy.exc import OperationalError
  from sqlalchemy.orm import Session, sessionmaker
  import caliban.config.experiment
  import caliban.util.auth
  from caliban.history.types import ContainerSpec, Experiment, ExperimentGroup, Job, JobSpec, JobStatus, Platform, init_db
  from caliban.platform.cloud.types import JobStatus
  from caliban.platform.gke.cluster import Cluster
  from caliban.platform.gke.types import JobStatus
  from caliban.platform.gke.util import default_credentials
label_desc: Use image node_id 3 for calling a global function with example usage: get_sql_engine(url, strict, echo) and returns: _create_sqa_engine, get_sql_engine, get_sql_engine