Improve conditions and refactor dataset classes (#475)

* Reimplement conditions

* Refactor datasets and implement LabelBatch

---------

Co-authored-by: Dario Coscia <dariocos99@gmail.com>

tests/test_solver/test_reduced_order_model_solver.py

@@ -3,7 +3,7 @@ import pytest
 
 from pina import Condition, LabelTensor
 from pina.problem import AbstractProblem
-from pina.condition import InputOutputPointsCondition
+from pina.condition import InputTargetCondition
 from pina.solver import ReducedOrderModelSolver
 from pina.trainer import Trainer
 from pina.model import FeedForward
@@ -16,8 +16,8 @@ class LabelTensorProblem(AbstractProblem):
     output_variables = ['u']
     conditions = {
         'data': Condition(
-            input_points=LabelTensor(torch.randn(20, 2), ['u_0', 'u_1']),
-            output_points=LabelTensor(torch.randn(20, 1), ['u'])),
+            input=LabelTensor(torch.randn(20, 2), ['u_0', 'u_1']),
+            target=LabelTensor(torch.randn(20, 1), ['u'])),
     }
 
 
@@ -26,8 +26,8 @@ class TensorProblem(AbstractProblem):
     output_variables = ['u']
     conditions = {
         'data': Condition(
-            input_points=torch.randn(20, 2),
-            output_points=torch.randn(20, 1))
+            input=torch.randn(20, 2),
+            target=torch.randn(20, 1))
     }
 
 
@@ -68,7 +68,7 @@ def test_constructor():
     ReducedOrderModelSolver(problem=LabelTensorProblem(),
                             reduction_network=reduction_net,
                             interpolation_network=interpolation_net)
-    assert ReducedOrderModelSolver.accepted_conditions_types == InputOutputPointsCondition
+    assert ReducedOrderModelSolver.accepted_conditions_types == InputTargetCondition
     with pytest.raises(SyntaxError):
         ReducedOrderModelSolver(problem=problem,
                                 reduction_network=AE_missing_encode(