Composing recordsets

Recordsets support some additional operations. We can check whether a record is included or not in a recordset. If x is a singleton recordset and my_recordset is a recordset containing many records, we can use the following:

• x in my_recordset
• x not in my_recordset

The following operations are also available:

• recordset.ids returns the list with the IDs of the recordset elements.
• recordset.ensure_one() checks whether it's a single record (singleton); if it's not, a ValueError exception is raised.
• recordset.filtered(func) returns a filtered recordset, and func can be a function or a dot-separated expression representing a path of fields to follow, as shown in the examples that follow.
• recordset.mapped(func) returns a list of mapped values. Instead of a function, a string of text can be used for the name of the field to map.
• recordset.sorted(func) returns an ordered recordset. Instead of a function, a string of text can be used for the name of the field to sort by. An optional reverse...