Used to distinguish a type's documents in the database.
Declare on fields or getter methods in order for them to be used in generated views filter conditions.
Declare on type in order specify a custom filter condition.
A TypeDiscriminator declared on type level cannot be mixed with TypeDiscriminators declared onb fields.
If TypeDiscriminator is declared on type level, a filter condition must be specified.
This condition is inserted along other conditions in the generated views map function:
function(doc) { if(CONDITION INSERTED HERE && doc.otherField) {emit(null, doc._id)} }
Not valid to use if declared on field or method level.