class_docstr: This handler handles connection and exectuin of Google BigQuery statements
code: def _get_account_keys(self):
      if "service_account_keys" in self.connection_data:
          if (
              os.path.isfile(
                  self.connection_data["service_account_keys"]
              )
              is False
          ):
              raise Exception(
                  "Service account keys' must be path to the file"
              )
          with open(
              self.connection_data["service_account_keys"]
          ) as source:
              info = json.load(source)
          return info
      elif "service_account_json" in self.connection_data:
          info = self.connection_data["service_account_json"]
          if not isinstance(info, dict):
              raise Exception("service_account_json has to be dict")
          info["private_key"] = info["private_key"].replace("\\n", "\n")
          return info
      else:
          raise Exception(
              "Connection args have to content ether service_account_json or service_account_keys"
          )
  
imports: import os
  import json
  from collections import OrderedDict
  from google.cloud import bigquery
  from google.oauth2 import service_account
  from sqlalchemy_bigquery.base import BigQueryDialect
  from mindsdb_sql.parser.ast.base import ASTNode
  from mindsdb_sql.render.sqlalchemy_render import SqlalchemyRender
  from mindsdb.integrations.libs.base import DatabaseHandler
  from mindsdb.integrations.libs.const import HANDLER_CONNECTION_ARG_TYPE
  from mindsdb.integrations.libs.response import HandlerStatusResponse, HandlerResponse, RESPONSE_TYPE
  from mindsdb.utilities import log
label_desc: Use image node_id 3 for calling the BigQueryHandler obj's underlying member method code with example usage: obj._get_account_keys() and returns: info, info