whole_func_string: function(input, it) {
        var output = input;
        var expr;
        while((expr = this.getExpr(output)) !== null) {
          var evalsTo = $parse(expr.expr)({it: it});
          output = output.substring(0, expr.start) + evalsTo + output.substring(expr.stop + 1);
        }
        return output;
      }
func_code_string: function(input, it) {
        var output = input;
        var expr;
        while((expr = this.getExpr(output)) !== null) {
          var evalsTo = $parse(expr.expr)({it: it});
          output = output.substring(0, expr.start) + evalsTo + output.substring(expr.stop + 1);
        }
        return output;
      }
func_documentation_string: substitutes all occurrences based in the it object