class_docstr: An annotation database instance.
  
  This class facilitates the annotation of genetic datasets with variant
  annotations. It accepts either an HTTP(S) URL to an Annotation DB
  configuration or a Python :obj:`dict` describing an Annotation DB
  configuration. User must specify the `region` (``'us'`` or ``'eu'``) in which
  the cluster is running if connecting to the default Hail Annotation DB.
  User must also specify the `cloud` platform that they are using (``'gcp'``
  or ``'aws'``).
  
  Parameters
  ----------
  region : :obj:`str`
      Region cluster is running in, either ``'us'`` or ``'eu'``
      (default is ``'us'``).
  cloud : :obj:`str`
      Cloud platform, either ``'gcp'`` or ``'aws'`` (default is ``'gcp'``).
  url : :obj:`str`, optional
      Optional URL to annotation DB configuration, if using custom configuration
      (default is ``None``).
  config : :obj:`str`, optional
      Optional :obj:`dict` describing an annotation DB configuration, if using
      custom configuration (default is ``None``).
  
  Note
  ----
  The ``'aws'`` `cloud` platform is currently only available for the ``'us'``
  `region`. If `region` is ``'eu'``, `cloud` must be set to ``'gcp'``.
  
  Examples
  --------
  Create an annotation database connecting to the default Hail Annotation DB:
  
  >>> db = hl.experimental.DB(region='us', cloud='gcp')
docstr: Check if datasets given in `names` are available in the annotation
  database instance.
  
  Parameters
  ----------
  names : :obj:`iterable`
      Names to check.
docstr_tok: ["Check","if","datasets","given","in","`","names","`","are","available","in","the","annotation","database","instance",".","Parameters","--","--","--","--","--","names",":",":","obj",":","`","iterable","`","Names","to","check","."]
code: def _check_availability(self, names: Iterable) -> None:
      """Check if datasets given in `names` are available in the annotation
      database instance.
  
      Parameters
      ----------
      names : :obj:`iterable`
          Names to check.
      """
      unavailable = [x for x in names if x not in self.__by_name.keys()]
      if unavailable:
          raise ValueError(
              f"datasets: {unavailable} not available"
              f" in the {self.region} region."
          )
  
imports: import json
  import os
  import warnings
  from typing import Iterable, List, Optional, Set, Tuple, Union
  import hail
  import pkg_resources
  from hailtop.utils import external_requests_client_session, retry_response_returning_functions
  from .lens import MatrixRows, TableRows
  from ..expr import StructExpression
  from ..matrixtable import MatrixTable, matrix_table_type
  from ..table import Table, table_type
  from ..typecheck import oneof, typecheck_method
  from ..utils.java import Env, info
label_desc: Use image node_id 6 for calling the DB obj's underlying member method code with example usage: obj._check_availability(names) without return types