text: import logging
  import mock
  from typing import Any, Dict, List, Set, Tuple, Optional, Sequence
  
  from django_auth_ldap.backend import LDAPBackend, _LDAPUser
  import django.contrib.auth
  from django.contrib.auth.backends import RemoteUserBackend
  from django.conf import settings
  from django.core.exceptions import ValidationError
  from django.core.validators import validate_email
  from django.http import HttpResponse
  from requests import HTTPError
  from social_core.backends.github import GithubOAuth2, GithubOrganizationOAuth2, \
      GithubTeamOAuth2
  from social_core.backends.base import BaseAuth
  from social_core.utils import handle_http_errors
  from social_core.exceptions import AuthFailed, SocialAuthBaseException
  from social_django.models import DjangoStorage
  from social_django.strategy import DjangoStrategy
  
  from zerver.lib.actions import do_create_user
  from zerver.lib.request import JsonableError
  from zerver.lib.subdomains import user_matches_subdomain, get_subdomain
  from zerver.lib.users import check_full_name
  from zerver.models import UserProfile, Realm, get_user_profile_by_id, \
      remote_user_to_email, email_to_username, get_realm, get_user
  
  def pad_method_dict(method_dict: Dict[str, bool]) -> Dict[str, bool]:
      """Pads an authentication methods dict to contain all auth backends
      supported by the software, regardless of whether they are
      configured on this server"""
      for key in AUTH_BACKEND_NAME_MAP:
          if key not in method_dict:
              method_dict[key] = False
      return method_dict
  
  def auth_enabled_helper(backends_to_check: List[str], realm: Optional[Realm]) -> bool:
      if realm is not None:
          enabled_method_dict = realm.authentication_methods_dict()
          pad_method_dict(enabled_method_dict)
      else:
          enabled_method_dict = dict((method, True) for method in Realm.AUTHENTICATION_FLAGS)
          pad_method_dict(enabled_method_dict)
      for supported_backend in django.contrib.auth.get_backends():
          for backend_name in backends_to_check:
              backend = AUTH_BACKEND_NAME_MAP[backend_name]
              if enabled_method_dict[backend_name] and isinstance(supported_backend, backend):
                  return True
      return False
  
  def ldap_auth_enabled(realm: Optional[Realm]=None) -> bool:
      return auth_enabled_helper(['LDAP'], realm)
  
  def email_auth_enabled(realm: Optional[Realm]=None) -> bool:
      return auth_enabled_helper(['Email'], realm)
  
  def password_auth_enabled(realm: Optional[Realm]=None) -> bool:
      return ldap_auth_enabled(realm) or email_auth_enabled(realm)
  
  def dev_auth_enabled(realm: Optional[Realm]=None) -> bool:
      return auth_enabled_helper(['Dev'], realm)
  
  def google_auth_enabled(realm: Optional[Realm]=None) -> bool:
      return auth_enabled_helper(['Google'], realm)
  
  def github_auth_enabled(realm: Optional[Realm]=None) -> bool:
      return auth_enabled_helper(['GitHub'], realm)
  
  def remote_auth_enabled(realm: Optional[Realm]=None) -> bool:
      return auth_enabled_helper(['RemoteUser'], realm)
  
  def any_oauth_backend_enabled(realm: Optional[Realm]=None) -> bool:
      """Used by the login page process to determine whether to show the
      'OR' for login with Google"""
      return auth_enabled_helper(['GitHub', 'Google'], realm)
  
  def require_email_format_usernames(realm: Optional[Realm]=None) -> bool:
      if ldap_auth_enabled(realm):
          if settings.LDAP_EMAIL_ATTR or settings.LDAP_APPEND_DOMAIN:
              return False
      return True
  
  def common_get_active_user(email: str, realm: Realm,
                             return_data: Dict[str, Any]=None) -> Optional[UserProfile]:
      try:
          user_profile = get_user(email, realm)
      except UserProfile.DoesNotExist:
          # If the user doesn't have an account in the target realm, we
          # check whether they might have an account in another realm,
          # and if so, provide a helpful error message via
          # `invalid_subdomain`.
          if not UserProfile.objects.filter(email__iexact=email).exists():
              return None
          if return_data is not None:
              return_data['invalid_subdomain'] = True
          return None
      if not user_profile.is_active:
          if return_data is not None:
              if user_profile.is_mirror_dummy:
                  # Record whether it's a mirror dummy account
                  return_data['is_mirror_dummy'] = True
              return_data['inactive_user'] = True
          return None
      if user_profile.realm.deactivated:
          if return_data is not None:
              return_data['inactive_realm'] = True
          return None
      return user_profile
  
  def generate_dev_ldap_dir(mode: str, num_users: int=8) -> Dict[str, Dict[str, Sequence[str]]]:
      mode = mode.lower()
      names = []
      for i in range(1, num_users+1):
          names.append(('LDAP User %d' % (i,), 'ldapuser%d@zulip.com' % (i,)))
  
      ldap_dir = {}
      if mode == 'a':
          for name in names:
              email = name[1].lower()
              email_username = email.split('@')[0]
              ldap_dir['uid=' + email + ',ou=users,dc=zulip,dc=com'] = {
                  'cn': [name[0], ],
                  'userPassword':  email_username,
              }
      elif mode == 'b':
          for name in names:
              email = name[1].lower()
              email_username = email.split('@')[0]
              ldap_dir['uid=' + email_username + ',ou=users,dc=zulip,dc=com'] = {
                  'cn': [name[0], ],
                  'userPassword': email_username,
              }
      elif mode == 'c':
          for name in names:
              email = name[1].lower()
              email_username = email.split('@')[0]
              ldap_dir['uid=' + email_username + ',ou=users,dc=zulip,dc=com'] = {
                  'cn': [name[0], ],
                  'userPassword': email_username + '_test',
                  'email': email,
              }
  
      return ldap_dir
  
  class ZulipAuthMixin:
      def get_user(self, user_profile_id: int) -> Optional[UserProfile]:
          """ Get a UserProfile object from the user_profile_id. """
          try:
              return get_user_profile_by_id(user_profile_id)
          except UserProfile.DoesNotExist:
              return None
  
  class ZulipDummyBackend(ZulipAuthMixin):
      """
      Used when we want to log you in without checking any
      authentication (i.e. new user registration or when otherwise
      authentication has already been checked earlier in the process).
      """
  
      def authenticate(self, username: Optional[str]=None, realm: Optional[Realm]=None,
                       use_dummy_backend: bool=False,
                       return_data: Dict[str, Any]=None) -> Optional[UserProfile]:
          if use_dummy_backend:
              # These are kwargs only for readability; they should never be None
              assert username is not None
              assert realm is not None
              return common_get_active_user(username, realm, return_data)
          return None
  
  class EmailAuthBackend(ZulipAuthMixin):
      """
      Email Authentication Backend
  
      Allows a user to sign in using an email/password pair rather than
      a username/password pair.
      """
  
      def authenticate(self, username: Optional[str]=None, password: Optional[str]=None,
                       realm: Optional[Realm]=None,
                       return_data: Optional[Dict[str, Any]]=None) -> Optional[UserProfile]:
          """ Authenticate a user based on email address as the user name. """
          if username is None or password is None:
              # Because of how we structure our auth calls to always
              # specify which backend to use when not using
              # EmailAuthBackend, username and password should always be set.
              raise AssertionError("Invalid call to authenticate for EmailAuthBackend")
          if realm is None:
              return None
          if not password_auth_enabled(realm):
              if return_data is not None:
                  return_data['password_auth_disabled'] = True
              return None
          if not email_auth_enabled(realm):
              if return_data is not None:
                  return_data['email_auth_disabled'] = True
              return None
  
          user_profile = common_get_active_user(username, realm, return_data=return_data)
          if user_profile is None:
              return None
          if user_profile.check_password(password):
              return user_profile
          return None
  
  class GoogleMobileOauth2Backend(ZulipAuthMixin):
      """
      Google Apps authentication for the legacy Android app.
      DummyAuthBackend is what's actually used for our modern Google auth,
      both for web and mobile (the latter via the mobile_flow_otp feature).
  
      Allows a user to sign in using a Google-issued OAuth2 token.
  
      Ref:
          https://developers.google.com/+/mobile/android/sign-in#server-side_access_for_your_app
          https://developers.google.com/accounts/docs/CrossClientAuth#offlineAccess
      """
  
      def authenticate(self, google_oauth2_token: str=None, realm: Optional[Realm]=None,
                       return_data: Optional[Dict[str, Any]]=None) -> Optional[UserProfile]:
          # We lazily import apiclient as part of optimizing the base
          # import time for a Zulip management command, since it's only
          # used in this one code path and takes 30-50ms to import.
          from apiclient.sample_tools import client as googleapiclient
          from oauth2client.crypt import AppIdentityError
          if realm is None:
              return None
          if return_data is None:
              return_data = {}
  
          if not google_auth_enabled(realm=realm):
              return_data["google_auth_disabled"] = True
              return None
  
          try:
              token_payload = googleapiclient.verify_id_token(google_oauth2_token, settings.GOOGLE_CLIENT_ID)
          except AppIdentityError:
              return None
  
          if token_payload["email_verified"] not in (True, "true"):
              return_data["valid_attestation"] = False
              return None
  
          return_data["valid_attestation"] = True
          return common_get_active_user(token_payload["email"], realm, return_data)
  
  class ZulipRemoteUserBackend(RemoteUserBackend):
      create_unknown_user = False
  
      def authenticate(self, remote_user: Optional[str], realm: Optional[Realm]=None,
                       return_data: Optional[Dict[str, Any]]=None) -> Optional[UserProfile]:
          assert remote_user is not None
          if realm is None:
              return None
          if not auth_enabled_helper(["RemoteUser"], realm):
              return None
  
          email = remote_user_to_email(remote_user)
          return common_get_active_user(email, realm, return_data=return_data)
  
  def email_belongs_to_ldap(realm: Realm, email: str) -> bool:
      if not ldap_auth_enabled(realm):
          return False
  
      # If we don't have an LDAP domain, it's impossible to tell which
      # accounts are LDAP accounts, so treat all of them as LDAP
      # accounts
      if not settings.LDAP_APPEND_DOMAIN:
          return True
  
      # Otherwise, check if the email ends with LDAP_APPEND_DOMAIN
      return email.strip().lower().endswith("@" + settings.LDAP_APPEND_DOMAIN)
  
  class ZulipLDAPException(_LDAPUser.AuthenticationFailed):
      """Since this inherits from _LDAPUser.AuthenticationFailed, these will
      be caught and logged at debug level inside django-auth-ldap's authenticate()"""
      pass
  
  class ZulipLDAPExceptionOutsideDomain(ZulipLDAPException):
      pass
  
  class ZulipLDAPConfigurationError(Exception):
      pass
  
  class ZulipLDAPAuthBackendBase(ZulipAuthMixin, LDAPBackend):
      # Don't use Django LDAP's permissions functions
      def has_perm(self, user: Optional[UserProfile], perm: Any, obj: Any=None) -> bool:
          # Using Any type is safe because we are not doing anything with
          # the arguments.
          return False
  
      def has_module_perms(self, user: Optional[UserProfile], app_label: Optional[str]) -> bool:
          return False
  
      def get_all_permissions(self, user: Optional[UserProfile], obj: Any=None) -> Set[Any]:
          # Using Any type is safe because we are not doing anything with
          # the arguments and always return empty set.
          return set()
  
      def get_group_permissions(self, user: Optional[UserProfile], obj: Any=None) -> Set[Any]:
          # Using Any type is safe because we are not doing anything with
          # the arguments and always return empty set.
          return set()
  
      def django_to_ldap_username(self, username: str) -> str:
          if settings.LDAP_APPEND_DOMAIN:
              if not username.endswith("@" + settings.LDAP_APPEND_DOMAIN):
                  raise ZulipLDAPExceptionOutsideDomain("Email %s does not match LDAP domain %s." % (
                      username, settings.LDAP_APPEND_DOMAIN))
              return email_to_username(username)
          return username
  
      def ldap_to_django_username(self, username: str) -> str:
          if settings.LDAP_APPEND_DOMAIN:
              return "@".join((username, settings.LDAP_APPEND_DOMAIN))
          return username
  
  class ZulipLDAPAuthBackend(ZulipLDAPAuthBackendBase):
      REALM_IS_NONE_ERROR = 1
  
      def __init__(self) -> None:
          if settings.DEVELOPMENT and settings.FAKE_LDAP_MODE:  # nocoverage # We only use this in development
              from fakeldap import MockLDAP
  
              ldap_patcher = mock.patch('django_auth_ldap.config.ldap.initialize')
              self.mock_initialize = ldap_patcher.start()
              self.mock_ldap = MockLDAP()
              self.mock_initialize.return_value = self.mock_ldap
  
              self.mock_ldap.directory = generate_dev_ldap_dir(settings.FAKE_LDAP_MODE,
                                                               settings.FAKE_LDAP_NUM_USERS)
  
      def authenticate(self, username: str, password: str, realm: Optional[Realm]=None,
                       return_data: Optional[Dict[str, Any]]=None) -> Optional[UserProfile]:
          if realm is None:
              return None
          self._realm = realm
          if not ldap_auth_enabled(realm):
              return None
  
          try:
              username = self.django_to_ldap_username(username)
          except ZulipLDAPExceptionOutsideDomain:
              return_data['outside_ldap_domain'] = True
              return None
  
          return ZulipLDAPAuthBackendBase.authenticate(self,
                                                       request=None,
                                                       username=username,
                                                       password=password)
  
      def get_or_build_user(self, username: str, ldap_user: _LDAPUser) -> Tuple[UserProfile, bool]:
          return_data = {}  # type: Dict[str, Any]
  
          if settings.LDAP_EMAIL_ATTR is not None:
              # Get email from ldap attributes.
              if settings.LDAP_EMAIL_ATTR not in ldap_user.attrs:
                  return_data["ldap_missing_attribute"] = settings.LDAP_EMAIL_ATTR
                  raise ZulipLDAPException("LDAP user doesn't have the needed %s attribute" % (
                      settings.LDAP_EMAIL_ATTR,))
  
              username = ldap_user.attrs[settings.LDAP_EMAIL_ATTR][0]
  
          user_profile = common_get_active_user(username, self._realm, return_data)
          if user_profile is not None:
              # An existing user, successfully authed; return it.
              return user_profile, False
  
          if return_data.get("inactive_realm"):
              # This happens if there is a user account in a deactivated realm
              raise ZulipLDAPException("Realm has been deactivated")
          if return_data.get("inactive_user"):
              raise ZulipLDAPException("User has been deactivated")
          if return_data.get("invalid_subdomain"):
              # TODO: Implement something in the caller for this to
              # provide a nice user-facing error message for this
              # situation (right now it just acts like any other auth
              # failure).
              raise ZulipLDAPException("Wrong subdomain")
          if self._realm.deactivated:
              # This happens if no account exists, but the realm is
              # deactivated, so we shouldn't create a new user account
              raise ZulipLDAPException("Realm has been deactivated")
  
          # We have valid LDAP credentials; time to create an account.
          full_name_attr = settings.AUTH_LDAP_USER_ATTR_MAP["full_name"]
          short_name = full_name = ldap_user.attrs[full_name_attr][0]
          try:
              full_name = check_full_name(full_name)
          except JsonableError as e:
              raise ZulipLDAPException(e.msg)
          if "short_name" in settings.AUTH_LDAP_USER_ATTR_MAP:
              short_name_attr = settings.AUTH_LDAP_USER_ATTR_MAP["short_name"]
              short_name = ldap_user.attrs[short_name_attr][0]
  
          user_profile = do_create_user(username, None, self._realm, full_name, short_name)
  
          return user_profile, True
  
  # Just like ZulipLDAPAuthBackend, but doesn't let you log in.
  class ZulipLDAPUserPopulator(ZulipLDAPAuthBackendBase):
      def authenticate(self, username: str, password: str, realm: Optional[Realm]=None,
                       return_data: Optional[Dict[str, Any]]=None) -> None:
          return None
  
  class DevAuthBackend(ZulipAuthMixin):
      # Allow logging in as any user without a password.
      # This is used for convenience when developing Zulip.
      def authenticate(self, dev_auth_username: Optional[str]=None, realm: Optional[Realm]=None,
                       return_data: Optional[Dict[str, Any]]=None) -> Optional[UserProfile]:
          assert dev_auth_username is not None
          if realm is None:
              return None
          if not dev_auth_enabled(realm):
              return None
          return common_get_active_user(dev_auth_username, realm, return_data=return_data)
  
  def social_associate_user_helper(backend: BaseAuth, return_data: Dict[str, Any],
                                   *args: Any, **kwargs: Any) -> Optional[UserProfile]:
      """Responsible for doing the Zulip-account lookup and validation parts
      of the Zulip Social auth pipeline (similar to the authenticate()
      methods in most other auth backends in this file).
      """
      subdomain = backend.strategy.session_get('subdomain')
      realm = get_realm(subdomain)
      if realm is None:
          return_data["invalid_realm"] = True
          return None
      return_data["realm"] = realm
  
      if not auth_enabled_helper([backend.auth_backend_name], realm):
          return_data["auth_backend_disabled"] = True
          return None
  
      if 'auth_failed_reason' in kwargs.get('response', {}):
          return_data["social_auth_failed_reason"] = kwargs['response']["auth_failed_reason"]
          return None
      elif hasattr(backend, 'get_verified_emails'):
          # Some social backends, like GitHubAuthBackend, don't guarantee that
          # the `details` data is validated.
          verified_emails = backend.get_verified_emails(*args, **kwargs)
          if len(verified_emails) == 0:
              # TODO: Provide a nice error message screen to the user
              # for this case, rather than just logging a warning.
              logging.warning("Social auth (%s) failed because user has no verified emails" %
                              (backend.auth_backend_name,))
              return_data["email_not_verified"] = True
              return None
          # TODO: ideally, we'd prompt the user for which email they
          # want to use with another pipeline stage here.
          validated_email = verified_emails[0]
      else:  # nocoverage
          # This code path isn't used by GitHubAuthBackend
          validated_email = kwargs["details"].get("email")
  
      if not validated_email:  # nocoverage
          # This code path isn't used with GitHubAuthBackend, but may be relevant for other
          # social auth backends.
          return_data['invalid_email'] = True
          return None
      try:
          validate_email(validated_email)
      except ValidationError:
          return_data['invalid_email'] = True
          return None
  
      return_data["valid_attestation"] = True
      return_data['validated_email'] = validated_email
      user_profile = common_get_active_user(validated_email, realm, return_data)
  
      if 'fullname' in kwargs["details"]:
          return_data["full_name"] = kwargs["details"]["fullname"]
      else:
          # If we add support for any of the social auth backends that
          # don't provide this feature, we'll need to add code here.
          raise AssertionError("Social auth backend doesn't provide fullname")
  
      return user_profile
  
  def social_auth_associate_user(
          backend: BaseAuth,
          *args: Any,
          **kwargs: Any) -> Dict[str, Any]:
      return_data = {}  # type: Dict[str, Any]
      user_profile = social_associate_user_helper(
          backend, return_data, *args, **kwargs)
  
      return {'user_profile': user_profile,
              'return_data': return_data}
  
  def social_auth_finish(backend: Any,
                         details: Dict[str, Any],
                         response: HttpResponse,
                         *args: Any,
                         **kwargs: Any) -> Optional[UserProfile]:
      from zerver.views.auth import (login_or_register_remote_user,
                                     redirect_and_log_into_subdomain)
  
      user_profile = kwargs['user_profile']
      return_data = kwargs['return_data']
  
      no_verified_email = return_data.get("email_not_verified")
      auth_backend_disabled = return_data.get('auth_backend_disabled')
      inactive_user = return_data.get('inactive_user')
      inactive_realm = return_data.get('inactive_realm')
      invalid_realm = return_data.get('invalid_realm')
      invalid_subdomain = return_data.get('invalid_subdomain')
      invalid_email = return_data.get('invalid_email')
      auth_failed_reason = return_data.get("social_auth_failed_reason")
  
      if invalid_realm:
          from zerver.views.auth import redirect_to_subdomain_login_url
          return redirect_to_subdomain_login_url()
      if auth_backend_disabled or inactive_user or inactive_realm or no_verified_email:
          # Redirect to login page. We can't send to registration
          # workflow with these errors. We will redirect to login page.
          return None
  
      if invalid_email:
          # In case of invalid email, we will end up on registration page.
          # This seems better than redirecting to login page.
          logging.warning(
              "{} got invalid email argument.".format(backend.auth_backend_name)
          )
          return None
  
      if auth_failed_reason:
          logging.info(auth_failed_reason)
          return None
  
      # Structurally, all the cases where we don't have an authenticated
      # email for the user should be handled above; this assertion helps
      # prevent any violations of that contract from resulting in a user
      # being incorrectly authenticated.
      assert return_data.get('valid_attestation') is True
  
      strategy = backend.strategy  # type: ignore # This comes from Python Social Auth.
      email_address = return_data['validated_email']
      full_name = return_data['full_name']
      is_signup = strategy.session_get('is_signup') == '1'
      redirect_to = strategy.session_get('next')
      realm = return_data["realm"]
  
      mobile_flow_otp = strategy.session_get('mobile_flow_otp')
      if mobile_flow_otp is not None:
          return login_or_register_remote_user(strategy.request, email_address,
                                               user_profile, full_name,
                                               invalid_subdomain=bool(invalid_subdomain),
                                               mobile_flow_otp=mobile_flow_otp,
                                               is_signup=is_signup,
                                               redirect_to=redirect_to)
      return redirect_and_log_into_subdomain(realm, full_name, email_address,
                                             is_signup=is_signup,
                                             redirect_to=redirect_to)
  
  class SocialAuthMixin(ZulipAuthMixin):
      def auth_complete(self, *args: Any, **kwargs: Any) -> Optional[HttpResponse]:
          """This is a small wrapper around the core `auth_complete` method of
          python-social-auth, designed primarily to prevent 500s for
          exceptions in the social auth code from situations that are
          really user errors.  Returning `None` from this function will
          redirect the browser to the login page.
          """
          try:
              # Call the auth_complete method of social_core.backends.oauth.BaseOAuth2
              return super().auth_complete(*args, **kwargs)  # type: ignore # monkey-patching
          except AuthFailed as e:
              # When a user's social authentication fails (e.g. because
              # they did something funny with reloading in the middle of
              # the flow), don't throw a 500, just send them back to the
              # login page and record the event at the info log level.
              logging.info(str(e))
              return None
          except SocialAuthBaseException as e:
              # Other python-social-auth exceptions are likely
              # interesting enough that we should log a warning.
              logging.warning(str(e))
              return None
  
  class GitHubAuthBackend(SocialAuthMixin, GithubOAuth2):
      auth_backend_name = "GitHub"
  
      def get_verified_emails(self, *args: Any, **kwargs: Any) -> List[str]:
          access_token = kwargs["response"]["access_token"]
          try:
              emails = self._user_data(access_token, '/emails')
          except (HTTPError, ValueError, TypeError):  # nocoverage
              # We don't really need an explicit test for this code
              # path, since the outcome will be the same as any other
              # case without any verified emails
              emails = []
  
          verified_emails = []
          for email_obj in emails:
              if not email_obj.get("verified"):
                  continue
              # TODO: When we add a screen to let the user select an email, remove this line.
              if not email_obj.get("primary"):
                  continue
              verified_emails.append(email_obj["email"])
  
          return verified_emails
  
      def user_data(self, access_token: str, *args: Any, **kwargs: Any) -> Dict[str, str]:
          """This patched user_data function lets us combine together the 3
          social auth backends into a single Zulip backend for GitHub Oauth2"""
          team_id = settings.SOCIAL_AUTH_GITHUB_TEAM_ID
          org_name = settings.SOCIAL_AUTH_GITHUB_ORG_NAME
  
          if team_id is None and org_name is None:
              # I believe this can't raise AuthFailed, so we don't try to catch it here.
              return super().user_data(
                  access_token, *args, **kwargs
              )
          elif team_id is not None:
              backend = GithubTeamOAuth2(self.strategy, self.redirect_uri)
              try:
                  return backend.user_data(access_token, *args, **kwargs)
              except AuthFailed:
                  return dict(auth_failed_reason="GitHub user is not member of required team")
          elif org_name is not None:
              backend = GithubOrganizationOAuth2(self.strategy, self.redirect_uri)
              try:
                  return backend.user_data(access_token, *args, **kwargs)
              except AuthFailed:
                  return dict(auth_failed_reason="GitHub user is not member of required organization")
  
          raise AssertionError("Invalid configuration")
  
  AUTH_BACKEND_NAME_MAP = {
      'Dev': DevAuthBackend,
      'Email': EmailAuthBackend,
      'GitHub': GitHubAuthBackend,
      'Google': GoogleMobileOauth2Backend,
      'LDAP': ZulipLDAPAuthBackend,
      'RemoteUser': ZulipRemoteUserBackend,
  }  # type: Dict[str, Any]
  