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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _perform_custom_queries(self, conn, custom_queries, tags, instance):
 """ Perform custom queries to collect additional metrics like number of result and duration of the query """

        for query in custom_queries:
            name = query.get("name")
            if name is None:
                self.log.error("`name` field is required for custom query")
                continue
            search_base = query.get("search_base")
            if search_base is None:
                self.log.error("`search_base` field is required for custom query #%s", name)
                continue
            search_filter = query.get("search_filter")
            if search_filter is None:
                self.log.error("`search_filter` field is required for custom query #%s", name)
                continue
            attrs = query.get("attributes")
            if "username" in query:
                username = query.get("username")
                password = query.get("password")
                if not username:
                    # username is an empty string, we want anonymous bind
                    username = None
                    password = None
            else:
                # username not specified, we want to reuse the credentials for the monitor backend
                username = instance.get("username")
                password = instance.get("password")

            try:
                # Rebind with different credentials
                auth_method = ldap3.SIMPLE if username else ldap3.ANONYMOUS
                if username is None:
                    conn.user = None
                res = conn.rebind(user=username, password=password, authentication=auth_method)
                if not res:
                    raise ldap3.core.exceptions.LDAPBindError("Error binding to server: {}".format(conn.result))
            except ldap3.core.exceptions.LDAPBindError:
                self.log.exception("Could not rebind to server at %s to perform query %s", instance.get("url"), name)
                continue

            try:
                # Perform the search query
                conn.search(search_base, search_filter, attributes=attrs)
            except ldap3.core.exceptions.LDAPException:
                self.log.exception("Unable to perform search query for %s", name)
                continue

            query_tags = ['query:{}'.format(name)]
            query_tags.extend(tags)
            query_time = self._get_query_time(conn)
            results = len(conn.entries)
            self.gauge("{}.query.duration".format(self.METRIC_PREFIX), query_time, tags=query_tags)
            self.gauge("{}.query.entries".format(self.METRIC_PREFIX), results, tags=query_tags)