se implementa un esquema para modelar el xml

FossilOrigin-Name: e4de658f60fe8fcbb330923e14958a5d8f8e0e6395db4f992ec7da45062fa193

facho/model/fields/field.py

@@ -0,0 +1,21 @@
+class Field:
+    def __set_name__(self, owner, name):
+        self.name = name
+
+    def __get__(self, inst, cls):
+        if inst is None:
+            return self
+        assert self.name is not None
+        return inst._fields[self.name]
+
+    def __set__(self, inst, value):
+        assert self.name is not None
+        inst._fields[self.name] = value
+
+    def _set_namespace(self, inst, name, namespaces):
+        if name is None:
+            return
+
+        if name not in namespaces:
+            raise KeyError("namespace %s not found" % (name))
+        inst._namespace_prefix = name