class_docstr: Creates a dataframe containing the lineage assoociations of a SageMaker object.
docstr: Given a job arn return the lineage entity.
  
  Args:
      job_arn (str): Arn of a training, processing, or transform job.
  
  Returns:
    str: The arn of the job's lineage entity.
docstr_tok: ["Given","a","job","arn","return","the","lineage","entity",".","Args",":","job_arn","(","str",")",":","Arn","of","a","training",",","processing",",","or","transform","job",".","Returns",":","str",":","The","arn","of","the","job","'s","lineage","entity","."]
code: def _get_start_arn_from_job_arn(self, job_arn: str) -> str:
      """Given a job arn return the lineage entity.
  
      Args:
          job_arn (str): Arn of a training, processing, or transform job.
  
      Returns:
        str: The arn of the job's lineage entity.
      """
      start_arn: str = None
      response: Any = (
          self._session.sagemaker_client.list_trial_components(
              SourceArn=job_arn
          )
      )
      trial_components: Any = response["TrialComponentSummaries"]
      if trial_components:
          start_arn = trial_components[0]["TrialComponentArn"]
      else:
          logging.warning("No trial components found for %s", job_arn)
      return start_arn
  
imports: from __future__ import absolute_import
  import logging
  from typing import Optional, Any, Iterator
  import pandas
  from pandas import DataFrame
  from sagemaker.lineage._api_types import AssociationSummary
  from sagemaker.lineage.association import Association
label_desc: Use image node_id 4 for calling the LineageTableVisualizer obj's underlying member method code with example usage: obj._get_start_arn_from_job_arn(job_arn) and returns: start_arn