code: def _parse_source_file_blob_key(blob_key):
      """Parse the BLOB key for accessing the content of a source file.
  
      Args:
        blob_key: The BLOB key to parse. By contract, it should have the format:
         `${SOURCE_FILE_BLOB_TAG_PREFIX}_${index}.${run_id}`
  
      Returns:
        - run ID, as a str.
        - File index, as an int.
      """
      key_body, run = blob_key.split(".", 1)
      index = int(key_body[len(SOURCE_FILE_BLOB_TAG_PREFIX) + 1 :])
      return run, index
  
imports: import json
  from tensorboard.data import provider
  from tensorboard.plugins.debugger_v2 import debug_data_multiplexer
label_desc: Use image node_id 18 for calling a global function with example usage: _parse_source_file_blob_key(blob_key) and returns: run,  index