Added define_fn

- updated write_fn_step to support attributes, bind names and
  explicit argument types
- added define_fn to generate write_fn_step sequences
- updated concatenate to define_fn as an example

Cargo.lock

@@ -298,6 +298,7 @@ dependencies = [
  "hashbrown 0.13.2",
  "itertools",
  "ordered-float",
+ "paste",
  "thiserror",
  "trait-set",
 ]
@@ -311,6 +312,12 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "paste"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f746c4065a8fa3fe23974dd82f15431cc8d40779821001404d10d2e79ca7d79"
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.56"