code: def _try_inject_s3_credentials(url):
      """
      Inject aws credentials into s3 url as s3://[aws_id]:[aws_key]:[bucket/][objectkey]
  
      If s3 url already contains secret key/id pairs, just return as is.
      """
      assert url.startswith("s3://")
      path = url[5:]
      # Check if the path already contains credentials
      tokens = path.split(":")
      # If there are two ':', its possible that we have already injected credentials
      if len(tokens) == 3:
          # Edge case: there are exactly two ':'s in the object key which is a false alarm.
          # We prevent this by checking that '/' is not in the assumed key and id.
          if ("/" not in tokens[0]) and ("/" not in tokens[1]):
              return url
  
      # S3 url does not contain secret key/id pair, query the environment variables
      (k, v) = _get_aws_credentials()
  
      # below is the form that turi customized, used in C++ impl.
      # s3://[access_key_id]:[secret_key]:[endpoint/]:[bucket]/[object_name]
      if path:
          return "s3://" + k + ":" + v + ":" + path
  
      raise ValueError("bucket not set for %s." % url)
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import os
  import urllib
  import re
  import itertools
  import uuid
  import datetime
  import sys
  from ._sframe_generation import generate_random_sframe
  from ._sframe_generation import generate_random_regression_sframe
  from ._sframe_generation import generate_random_classification_sframe
  from ._type_checks import _raise_error_if_not_of_type
  from ._type_checks import _is_non_string_iterable
  from ._progress_table_printer import ProgressTablePrinter
label_desc: Use image node_id 4 for calling a global function with example usage: _try_inject_s3_credentials(url) and returns: unknown, url