text: from flask import current_app as app
  from threading import Lock
  from werkzeug.utils import import_string
  
  from amundsen_application.base.base_issue_tracker_client import BaseIssueTrackerClient
  
  _issue_tracker_client = None
  _issue_tracker_client_lock = Lock()
  
  
  def get_issue_tracker_client() -> BaseIssueTrackerClient:
      """
      Provides singleton proxy client based on the config
      :return: Proxy instance of any subclass of BaseProxy
      """
      global _issue_tracker_client
  
      if _issue_tracker_client:
          return _issue_tracker_client
  
      with _issue_tracker_client_lock:
          if _issue_tracker_client:
              return _issue_tracker_client
          else:
              # Gather all the configuration to create an IssueTrackerClient
              if app.config['ISSUE_TRACKER_CLIENT_ENABLED']:
                  url = app.config['ISSUE_TRACKER_URL']
                  user = app.config['ISSUE_TRACKER_USER']
                  password = app.config['ISSUE_TRACKER_PASSWORD']
                  project_id = app.config['ISSUE_TRACKER_PROJECT_ID']
                  max_results = app.config['ISSUE_TRACKER_MAX_RESULTS']
  
                  if app.config['ISSUE_TRACKER_CLIENT']:
                      client = import_string(app.config['ISSUE_TRACKER_CLIENT'])
                      _issue_tracker_client = client(issue_tracker_url=url,
                                                     issue_tracker_user=user,
                                                     issue_tracker_password=password,
                                                     issue_tracker_project_id=project_id,
                                                     issue_tracker_max_results=max_results)
  
      return _issue_tracker_client
  