code: def lookup_bucket(bucket_name):
      """Lookup a bucket by name in the global collection.
  
      :param bucket_name:str the name of the Bucket.
      :return: the bucket matching the name.
      :rtype:GcsBucket
      :raises:ErrorResponse if the bucket is not found.
      """
      bucket = GCS_BUCKETS.get(bucket_name)
      if bucket is None:
          raise error_response.ErrorResponse(
              "Bucket %s not found" % bucket_name, status_code=404
          )
      return bucket
  
imports: import base64
  import error_response
  import hashlib
  import json
  import random
  import re
label_desc: Use image node_id 7 for calling a global function with example usage: lookup_bucket(bucket_name) and returns: bucket