Docs for DAL.validators_method.im_class

    An instance of this class represents a database connection

    Args:
        uri(str): contains information for connecting to a database.
            Defaults to `'sqlite://dummy.db'`

            Note:
                experimental: you can specify a dictionary as uri
                parameter i.e. with::

                    db = DAL({"uri": "sqlite://storage.sqlite",
                              "tables": {...}, ...})

                for an example of dict input you can check the output
                of the scaffolding db model with

                    db.as_dict()

                Note that for compatibility with Python older than
                version 2.6.5 you should cast your dict input keys
                to str due to a syntax limitation on kwarg names.
                for proper DAL dictionary input you can use one of::

                    obj = serializers.cast_keys(dict, [encoding="utf-8"])
                    #or else (for parsing json input)
                    obj = serializers.loads_json(data, unicode_keys=False)

        pool_size: How many open connections to make to the database object.
        folder: where .table files will be created. Automatically set within
            web2py. Use an explicit path when using DAL outside web2py
        db_codec: string encoding of the database (default: 'UTF-8')
        table_hash: database identifier with .tables. If your connection hash
                    change you can still using old .tables if they have db_hash
                    as prefix
        check_reserved: list of adapters to check tablenames and column names
            against sql/nosql reserved keywords. Defaults to `None`

            - 'common' List of sql keywords that are common to all database
              types such as "SELECT, INSERT". (recommended)
            - 'all' Checks against all known SQL keywords
            - '<adaptername>'' Checks against the specific adapters list of
              keywords
            - '<adaptername>_nonreserved' Checks against the specific adapters
              list of nonreserved keywords. (if available)

        migrate: sets default migrate behavior for all tables
        fake_migrate: sets default fake_migrate behavior for all tables
        migrate_enabled: If set to False disables ALL migrations
        fake_migrate_all: If set to True fake migrates ALL tables
        attempts: Number of times to attempt connecting
        auto_import: If set to True, tries import automatically table
            definitions from the databases folder (works only for simple models)
        bigint_id: If set, turn on bigint instead of int for id and reference
            fields
        lazy_tables: delays table definition until table access
        after_connection: can a callable that will be executed after the
            connection

    Example:
        Use as::

           db = DAL('sqlite://test.db')

        or::

           db = DAL(**{"uri": ..., "tables": [...]...}) # experimental

           db.define_table('tablename', Field('fieldname1'),
                                        Field('fieldname2'))