code: def __init__(self, dashboard_head):
      super().__init__(dashboard_head)
      self.http_session = aiohttp.ClientSession()
      self._session_name = dashboard_head.session_name
      self.prometheus_host = os.environ.get(
          PROMETHEUS_HOST_ENV_VAR, DEFAULT_PROMETHEUS_HOST
      )
  
file_path: ray/dashboard/modules/data/data_head.py
imports: import json
  import os
  from enum import Enum
  import aiohttp
  from aiohttp.web import Request, Response
  import ray.dashboard.optional_utils
  import ray.dashboard.utils
  from ray.dashboard.modules.metrics.metrics_head import PROMETHEUS_HOST_ENV_VAR, DEFAULT_PROMETHEUS_HOST, PrometheusQueryError
  from urllib.parse import quote
  import ray
  import logging
label_desc: Use image node_id 1 to create a new DataHead object from inherited base classes: dashboard_utils with example: obj = DataHead(dashboard_head)