Add Supervised Problem (#451)

* Add SuperviedProblem class in problem zoo

pina/problem/zoo/supervised_problem.py

@@ -0,0 +1,37 @@
+from pina.problem import AbstractProblem
+from pina import Condition
+from pina import Graph
+
+class SupervisedProblem(AbstractProblem):
+    """
+    A problem definition for supervised learning in PINA.
+
+    This class allows an easy and straightforward definition of a Supervised problem,
+    based on a single condition of type `InputOutputPointsCondition`
+
+    :Example:
+        >>> import torch
+        >>> input_data = torch.rand((100, 10))
+        >>> output_data = torch.rand((100, 10))
+        >>> problem = SupervisedProblem(input_data, output_data)
+    """
+    conditions = dict()
+    output_variables = None
+
+    def __init__(self, input_, output_):
+        """
+        Initialize the SupervisedProblem class
+
+        :param input_: Input data of the problem
+        :type input_: torch.Tensor | Graph
+        :param output_: Output data of the problem
+        :type output_: torch.Tensor
+        """
+        if isinstance(input_, Graph):
+            input_ = input_.data
+        self.conditions['data'] = Condition(
+            input_points=input_,
+            output_points = output_
+        )
+        super().__init__()
+