great-expectations - MissingConfigVariableError while creating DataContext in Great Expectations

Question

1. Unable to create DataContext with the following configuration.I am try to use a Databricks spark df datasource and in house DB as storeBackendDefaults
2. I get the MissingConfigVariableError exceptions
3. Could some explain what I am missing

import great_expectations as ge
import great_expectations.exceptions as ge_exceptions
from great_expectations.data_context.types.base import DataContextConfig, DatasourceConfig, FilesystemStoreBackendDefaults, DatabaseStoreBackendDefaults
from great_expectations.data_context import BaseDataContext

my_spark_datasource_config = DatasourceConfig(
    class_name="Datasource",
    execution_engine={"class_name": "SparkDFExecutionEngine"},
    data_connectors={"sample_sparkdf_runtime_data_connector": {
            "module_name": "great_expectations.datasource.data_connector",
            "class_name": "RuntimeDataConnector",
            "batch_identifiers": [
                "some_key_maybe_pipeline_stage",
                "some_other_key_maybe_run_id"
            ]
        }
    }
)


data_context_config = DataContextConfig(config_version = 2
                                        ,plugins_directory = None
                                        ,config_variables_file_path = None
                                        ,datasources={"my_spark_datasource": my_spark_datasource_config}
                                        ,store_backend_defaults=DatabaseStoreBackendDefaults(default_credentials = {
                                                                                                                      "drivername": "PrestoSQL",
                                                                                                                      "host": "*****",
                                                                                                                      "port": "443",
                                                                                                                      "username": "*****",
                                                                                                                      "password": "*****",
                                                                                                                      "database": "****"
                                                                                                                    }
                                                                                            ),
    anonymous_usage_statistics={"enabled": False}
                                      )

context = BaseDataContext(project_config=data_context_config)