How to use the ovs.db function in ovs

def get_simple_printable_row_string(row, columns):
    s = ""
    for column in columns:
        if hasattr(row, column) and not (type(getattr(row, column))
                                         is ovs.db.data.Atom):
            value = getattr(row, column)
            if isinstance(value, dict):
                value = sorted(value.items())
            s += "%s=%s " % (column, value)
    s = s.strip()
    s = re.sub('""|,|u?\'', "", s)
    s = re.sub(r'UUID\(([^)]+)\)', r'\1', s)
    s = re.sub('False', 'false', s)
    s = re.sub('True', 'true', s)
    s = re.sub(r'(ba)=([^[][^ ]*) ', r'\1=[\2] ', s)
    return s

def atom_from_string(base, value_string, symtab=None):
    type_ = base.type
    atom = None
    if type_ == ovs.db.types.IntegerType:
        atom = ovs.db.data.Atom(type_, int(value_string))
    elif type_ == ovs.db.types.RealType:
        # TODO:XXX negation
        atom = ovs.db.data.Atom(
            type_, ovs.db.parser.float_to_int(float(value_string)))
    elif type_ == ovs.db.types.BooleanType:
        if value_string in ("true", "yes", "on", "1"):
            atom = ovs.db.data.Atom(type_, True)
        elif value_string == ("false", "no", "off", "0"):
            atom = ovs.db.data.Atom(type_, False)
    elif type_ == ovs.db.types.StringType:
        # TODO:XXXX escape: if value_string[0] == '"':
        atom = ovs.db.data.Atom(type_, value_string)
    elif type_ == ovs.db.types.UuidType:
        if value_string[0] == "@":
            assert symtab is not None

for uuid_string, row_update in table_update.iteritems():
                if not ovs.ovsuuid.is_valid_string(uuid_string):
                    raise error.Error(' for table "%s" '
                                      'contains bad UUID "%s" as member '
                                      'name' % (table_name, uuid_string),
                                      table_update)
                uuid = ovs.ovsuuid.from_string(uuid_string)

                if type(row_update) != dict:
                    raise error.Error(' for table "%s" '
                                      'contains  for %s that '
                                      'is not an object'
                                      % (table_name, uuid_string))

                parser = ovs.db.parser.Parser(row_update, "row-update")
                old = parser.get_optional("old", [dict])
                new = parser.get_optional("new", [dict])
                parser.finish()

                if not old and not new:
                    raise error.Error(' missing "old" and '
                                      '"new" members', row_update)

                if self.__process_update(table, uuid, old, new):
                    self.change_seqno += 1

def __create_row(self, table, uuid):
        data = {}
        for column in table.columns.itervalues():
            data[column.name] = ovs.db.data.Datum.default(column.type)
        row = table.rows[uuid] = Row(self, table, uuid, data)
        return row

column_schema = ovsrec_row._table.columns[column]
        if key is not None:
            value_json = ['map', [[key, value_json]]]
            if column_schema.type.value.type == ovs.db.types.VoidType:
                vsctl_fatal('cannot specify key to set for non-map column %s' %
                            column)
            datum = ovs.db.data.Datum.from_json(column_schema.type, value_json,
                                                self.symtab)
            values = getattr(ovsrec_row, column, {})
            values.update(datum.to_python(ovs.db.idl._uuid_to_row))
            setattr(ovsrec_row, column, values)
        else:
            datum = ovs.db.data.Datum.from_json(column_schema.type, value_json,
                                                self.symtab)
            setattr(ovsrec_row, column,
                    datum.to_python(ovs.db.idl._uuid_to_row))

def atom_from_string(base, value_string, symtab=None):
    type_ = base.type
    atom = None
    if type_ == ovs.db.types.IntegerType:
        atom = ovs.db.data.Atom(type_, int(value_string))
    elif type_ == ovs.db.types.RealType:
        # TODO:XXX negation
        atom = ovs.db.data.Atom(
            type_, ovs.db.parser.float_to_int(float(value_string)))
    elif type_ == ovs.db.types.BooleanType:
        if value_string in ("true", "yes", "on", "1"):
            atom = ovs.db.data.Atom(type_, True)
        elif value_string == ("false", "no", "off", "0"):
            atom = ovs.db.data.Atom(type_, False)
    elif type_ == ovs.db.types.StringType:
        # TODO:XXXX escape: if value_string[0] == '"':
        atom = ovs.db.data.Atom(type_, value_string)
    elif type_ == ovs.db.types.UuidType:
        if value_string[0] == "@":
            assert symtab is not None

def __column_name(self, column):
        if column.type.key.type == ovs.db.types.UuidType:
            return ovs.ovsuuid.to_json(column.type.key.type.default)
        else:
            return column.type.key.type.default

if type(name) != list and name == record_id:
                    if (referrer):
                        vsctl_fatal('multiple rows in %s match "%s"' %
                                    (table_name, record_id))
                    referrer = ovsrec_row

        if not referrer:
            return None

        final = None
        if vsctl_row_id.uuid_column:
            referrer.verify(vsctl_row_id.uuid_column)
            uuid = getattr(referrer, vsctl_row_id.uuid_column)

            uuid_ = referrer._data[vsctl_row_id.uuid_column]
            assert uuid_.type.key.type == ovs.db.types.UuidType
            assert uuid_.type.value is None
            assert type(uuid) == list

            if len(uuid) == 1:
                final = uuid[0]
        else:
            final = referrer

        return final

def from_json(json, symtab=None):
    try:
        s = ovs.db.parser.unwrap_json(json, "uuid", six.string_types, "string")
        if not uuidRE.match(s):
            raise error.Error("\"%s\" is not a valid UUID" % s, json)
        return uuid.UUID(s)
    except error.Error as e:
        if not symtab:
            raise e
        try:
            name = ovs.db.parser.unwrap_json(json, "named-uuid",
                                             six.string_types, "string")
        except error.Error:
            raise e

        if name not in symtab:
            symtab[name] = uuid.uuid4()
        return symtab[name]