Extracting features with equal field value using graphical modeler of QGIS

Is it possible to automate the following procedure with graphical modeler in qgis 3.4 or is it easier to perform such action with a python script using PyQGIS?

1. Identify a feature (a line) in a vector layer using the mouse pointer, features have an attribute named RLID
2. Then let the model select all features with the same attribute value in the vector layer

Right now this is done manually, a very time-consuming process. The manual process starts by identifying a feature and copying the RLID attribute value. Then the features with the same RLID value are selected using “Select features by value”.

I am completely new to qgis but know how to program with python.

Speed is important since we have 200k features to process. I tried a little python script (with a selected feature) for extracting features with the same attribute value and it took 30s, which is very long time compared with F3 – Select features by value.

layer = iface.activeLayer();
features = layer.getFeatures()
selected = layer.getSelectedFeatures()
for f in selected:
    rlid = f['RLID']
    print(rlid)

fs = [f.id() for f in features if f['RLID'] == rlid]
print(fs)

Found by older posts that a quicker way to obtain the features fs is:

expr = QgsExpression( ""RLID"='"+rlid+"'" )
it = layer.getFeatures( QgsFeatureRequest( expr ) )
fs = [i.id() for i in it]