search_quantities from class properties

[sanbrock]

Search quantities are collected via traversing the Entry. Problems:

• an object is visited only once. Hence, if an object is assigned to different nodes in the tree, its properties are made searchable under only one name (or concept).
• properties are collected from object instances and not from the class properties. Hence, properties are listed under a name (or concept) also if they would not belong to that concept (but only to a specialised and extended concept).

Eg:

• if Entry is a subclass of Step, and data.Em.steps[0]=data.Em.ENTRY[0]
  data.Em.steps.xxx is collected, but
  data.Em.ENTRY.xxx is not.
• if Step.xxx is defined, but Steps.yyy is not, and Entry.yyy is defined
  data.ENTRY.xxx,
  data.ENTRY.yyy, and
  data.steps.xxx
  shall be collected, but
  data.steps.yyy
  shall not be collected for searchability.

Solution:

• traversing shall visit the same object even multiple times if it appears multiple times in the tree (but only once along a specific branch - to avoid endless loops)
• only class properties shall be collected as search_quantities, and not all object properties.

[sanbrock]

an alternative:
create a copy instead of using a python reference:
steps[0]=ENTRY[0].m_copy()