code: def _try_inject_s3_credentials(url):
      
      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()
      return 's3://' + k + ':' + v + ':' + path
docs: 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.