[FEATURE] lookup functions for ID's from the C++ core

[TonyXiang8787]

Intention

When we have the calculation results, it is in a numpy structured array. For example for the node you have:

Input
id    u_pu    ...
 7     1.05    ...
 10   1.07    ...
 8   1.07    ...
103  1.0      ...

Say we want to retrieve a sub-array with node id 10 and 103. To do this, we need to translate the list of id's to list of position numbers in the original numpy array. The C++ core already has hash table to do the lookup.

API

Say we have a numpy array a = [10, 103]. We should be able to retrieve the position number by using the following call:

position = model.get_indexer('node', a)

The returned value should be [1, 3].

We can then for example to retrieve the u_pu for these two nodes by:

u_pu_sub_array = node_result['u_pu'][position]

The result u_pu_sub_array should be [1.07, 1.0]