Add info about 250 graphs

Author: aurorarossi

GraphNeuralNetworks/docs/src/tutorials/temporal_graph_classification.md

@@ -39,7 +39,7 @@ dataset TemporalBrains:
 ````
 
 After loading the dataset from the MLDatasets.jl package, we see that there are 1000 graphs and we need to convert them to the `TemporalSnapshotsGNNGraph` format.
-So we create a function called `data_loader` that implements the latter and splits the dataset into the training set that will be used to train the model and the test set that will be used to test the performance of the model.
+So we create a function called `data_loader` that implements the latter and splits the dataset into the training set that will be used to train the model and the test set that will be used to test the performance of the model. Due to computational costs, we use only 250 out of the original 1000 graphs, 200 for training and 50 for testing.
 
 ````julia
 function data_loader(brain_dataset)

GraphNeuralNetworks/docs/src_tutorials/introductory_tutorials/temporal_graph_classification.jl

@@ -32,7 +32,7 @@ Random.seed!(17); # for reproducibility
 brain_dataset = TemporalBrains()
 
 # After loading the dataset from the MLDatasets.jl package, we see that there are 1000 graphs and we need to convert them to the `TemporalSnapshotsGNNGraph` format.
-# So we create a function called `data_loader` that implements the latter and splits the dataset into the training set that will be used to train the model and the test set that will be used to test the performance of the model.
+# So we create a function called `data_loader` that implements the latter and splits the dataset into the training set that will be used to train the model and the test set that will be used to test the performance of the model. Due to computational costs, we use only 250 out of the original 1000 graphs, 200 for training and 50 for testing.
 
 
 function data_loader(brain_dataset)