ORM: Add unary operations +, - and abs to NumericType (#5946)

Three unary operations are added to the `NumericType` data subclass:

* `+`: Implemented through `__pos__`
* `-`: Implemented through `__neg__`
* `abs`: Implemented through `__abs__`

The `__pos__` dunder overloads the unary plus operator `+` and returns
the value of the object as-is, whereas the `__neg__` overloads the unary
minus operator `-` and returns a new instance of the same class with the
negation of the value of the original object. The `__abs__` dunder is
called when the object is passed to the `abs` built-in and returns the
absolute value.

.gitignore

@@ -17,6 +17,7 @@
 .eggs
 .vscode
 .tox
+Pipfile
 
 # files created by coverage
 .cache

aiida/orm/nodes/data/numeric.py

@@ -124,3 +124,12 @@ def __float__(self):
 
     def __int__(self):
         return int(self.value)
+
+    def __pos__(self):
+        return self.value
+
+    def __neg__(self):
+        return self.new(-self.value)
+
+    def __abs__(self):
+        return abs(self.value)

tests/orm/nodes/data/test_base.py

@@ -214,3 +214,45 @@ def test_equality(node_type, a, b):
     # Test equality comparison with other `BaseType` nodes
     assert node_a == node_a_clone
     assert node_a != node_b
+
+
+@pytest.mark.parametrize('numeric_type', (Float, Int))
+def test_unary_pos(numeric_type):
+    """Test the ``__pos__`` unary operator for all ``NumericType`` subclasses."""
+
+    node_positive = numeric_type(1)
+    node_negative = numeric_type(-1)
+
+    assert +node_positive == node_positive
+    assert +node_negative == node_negative
+
+
+@pytest.mark.parametrize('numeric_type', (Float, Int))
+def test_unary_neg(numeric_type):
+    """Test the ``__neg__`` unary operator for all ``NumericType`` subclasses."""
+
+    node_positive = numeric_type(1)
+    node_negative = numeric_type(-1)
+
+    assert -node_positive != node_positive
+    assert -node_negative != node_negative
+    assert -node_positive == node_negative
+    assert -node_negative == node_positive
+    assert -node_negative == node_positive
+
+
+@pytest.mark.parametrize('numeric_type', (Float, Int))
+def test_unary_abs(numeric_type):
+    """Test the ``__abs__`` unary operator for all ``NumericType`` subclasses"""
+
+    node_positive = numeric_type(1)
+    node_negative = numeric_type(-1)
+
+    # Test positive number
+    abs_positive = abs(node_positive)
+    assert abs_positive == node_positive
+
+    # Test negative number
+    abs_negative = abs(node_negative)
+    assert abs_negative != node_negative
+    assert abs_positive == abs_negative