document model R abstraction

src/tea3/tea3model.py

@@ -30,6 +30,12 @@ class Tea3Model:
         self.g = self.v[-1]
 
     def _abstract_R(self):
+        """
+        Abstract all monomials involving intermediate R variables.
+
+        For each polynomial in ``R_bits``, monomials containing any ``R`` or ``g`` variable are replaced with a variable ``g``.
+        Monomials involving only ``x``, ``y``, and ``r`` variables are kept unchanged.
+        """
         one  = self.S.one()
         zero = self.S.zero()