code: def _process_query(self, endpoint_name, start):
      self.logger.log(
          logging.DEBUG, f"Processing query {endpoint_name}..."
      )
      try:
          self._add_CORS_header()
  
          if not self.request.body:
              self.request.body = {}
  
          # extract request data explicitly for caching purpose
          request_json = self.request.body.decode("utf-8")
  
          # Sanitize input data
          data = self._sanitize_request_data(json.loads(request_json))
      except Exception as e:
          self.logger.log(logging.ERROR, str(e))
          err_msg = format_exception(e, "Invalid Input Data")
          self.error_out(400, err_msg)
          return
  
      try:
          (po_name, _) = self._get_actual_model(endpoint_name)
  
          # po_name is None if self.python_service.ps.query_objects.get(
          # endpoint_name) is None
          if not po_name:
              self.error_out(
                  404,
                  "UnknownURI",
                  info=f"Endpoint '{endpoint_name}' does not exist",
              )
              return
  
          po_obj = self.python_service.ps.query_objects.get(po_name)
  
          if not po_obj:
              self.error_out(
                  404,
                  "UnknownURI",
                  info=f'Endpoint "{po_name}" does not exist',
              )
              return
  
          if po_name != endpoint_name:
              self.logger.log(
                  logging.INFO,
                  f"Querying actual model: po_name={po_name}",
              )
  
          uid = _get_uuid()
  
          # record query w/ request ID in query log
          qry = Query(po_name, request_json)
          gls_time = 0
          # send a query to PythonService and return
          (gls_time, _) = self._handle_result(po_name, data, qry, uid)
  
          # if error occurred, GLS time is None.
          if not gls_time:
              return
  
      except Exception as e:
          self.logger.log(logging.ERROR, str(e))
          err_msg = format_exception(e, "process query")
          self.error_out(500, "Error processing query", info=err_msg)
          return
  
imports: from tabpy.tabpy_server.handlers import BaseHandler
  import logging
  import time
  from tabpy.tabpy_server.common.messages import Query, QuerySuccessful, QueryError, UnknownURI
  from hashlib import md5
  import uuid
  import json
  from tabpy.tabpy_server.common.util import format_exception
  import urllib
  from tornado import gen
  from tabpy.tabpy_server.handlers.util import AuthErrorStates
label_desc: Use image node_id 6 for calling the QueryPlaneHandler obj's underlying member method code with example usage: obj._process_query(endpoint_name, start) without return types