bench parsing docs

src/kyupy/bench.py

@@ -5,6 +5,10 @@ Historically it was first used in the
 `ISCAS89 benchmark set <https://people.engr.ncsu.edu/brglez/CBL/benchmarks/ISCAS89/>`_.
 Besides loading these benchmarks, this module is also useful for easily constructing simple circuits:
 ``c = bench.parse('input(x, y) output(a, o, n) a=and(x,y) o=or(x,y) n=not(x)')``.
+
+This parser automatically translates gate to simulation primitives supported by kyupy.
+In most cases this means just adding the number of inputs to the name: e.g. NAND -> NAND2, OR -> OR4, INV -> INV1.
+Since simulators only support at most four-input-gates, gates with more than four inputs are implemented as tree.
 """
 
 from lark import Lark, Transformer