When Joining or Transforming properties, we should use 3 methods:
Collection joinPropertiesAllowingSplit(Object property1, Object property2, ...)
Object joinPropertiesByTransforming(Object property1, Object property2, ...)
Object transformProperty(Object property)
First method allows, as it's name says, allows to separate properties after they have been joined.
Second method allows to join multiple properties forming new object with properties derived from input properties.
Thrid method allows to transform single property into another property.