Adding a generic atom mapping scorer

gufe/mapping/atom_mapping_scorer.py

@@ -0,0 +1,42 @@
+# This code is part of kartograf and is licensed under the MIT license.
+# For details, see https://github.com/OpenFreeEnergy/gufe
+
+import abc
+
+from . import AtomMapping
+
+
+class AtomMappingScorer(abc.ABC):
+    """A generic class for scoring Atom mappings.
+    this class can be used for example to build graph algorithm based networks.
+
+    Implementations of this class can require an arbitrary and non-standardised
+    number of input arguments to create.
+
+    Implementations of this class provide the :meth:`.get_score` method
+
+    """
+
+    def __call__(self, mapping: AtomMapping) -> float:
+        return self.get_score(mapping)
+
+    @abc.abstractmethod
+    def get_score(self, mapping: AtomMapping) -> float:
+        """ calculate the score for an  :class:`.AtomMapping`
+            the scoring function returns a value between 0 and 1.
+            a value close to 1.0 indicates a small distance, a score close to zero indicates a large cost/error.
+
+        Parameters
+        ----------
+        mapping: AtomMapping
+            the mapping to be scored
+        args
+        kwargs
+
+        Returns
+        -------
+        float
+            a value between [0,1] where one is a very bad score and 0 a very good one.
+
+        """
+        pass