docs: function toJSON(form) {
      if(isList(form)) {
          var json = [];
  // DELETE if(!form.formEach) { return json; }
          form.forEach(function(node) {
            var childJSON = toJSON(node);
            // scrub no-op "nop" expressions from the output
            // (nop is mainly just for "prelude" comments to hang on)
            if(!(Array.isArray(childJSON) && childJSON[0] === "nop")) {
              json.push(childJSON);
            }
          })
          return json;
      }
      else if(isAtom(form)) {
         return valueOf(form);
      }
      else {
          throw new Error('Unknown form type in toJSON for node: ' + form);
      }
  }