Add Supervised Problem (#451)

* Add SuperviedProblem class in problem zoo

tests/test_problem_zoo/test_supervised_problem.py

@@ -0,0 +1,31 @@
+import torch
+from pina.problem import AbstractProblem
+from pina.condition import InputOutputPointsCondition
+from pina.problem.zoo.supervised_problem import SupervisedProblem
+from pina import RadiusGraph
+
+def test_constructor():
+    input_ = torch.rand((100,10))
+    output_ = torch.rand((100,10))
+    problem = SupervisedProblem(input_=input_, output_=output_)
+    assert isinstance(problem, AbstractProblem)
+    assert hasattr(problem, "conditions")
+    assert isinstance(problem.conditions, dict)
+    assert list(problem.conditions.keys()) == ['data']
+    assert isinstance(problem.conditions['data'], InputOutputPointsCondition)
+
+def test_constructor_graph():
+    x = torch.rand((20,100,10))
+    pos = torch.rand((20,100,2))
+    input_ = RadiusGraph(
+        x=x, pos=pos, r=.2, build_edge_attr=True
+    )
+    output_ = torch.rand((100,10))
+    problem = SupervisedProblem(input_=input_, output_=output_)
+    assert isinstance(problem, AbstractProblem)
+    assert hasattr(problem, "conditions")
+    assert isinstance(problem.conditions, dict)
+    assert list(problem.conditions.keys()) == ['data']
+    assert isinstance(problem.conditions['data'], InputOutputPointsCondition)
+    assert isinstance(problem.conditions['data'].input_points, list) 
+    assert isinstance(problem.conditions['data'].output_points, torch.Tensor)