lib/base.js
function extraction(o) {
      return _.map(o, function (spec, field) {
        var fn = _.extract(spec, ['mutators', direction]) || _.identity;
        return [field, fn];
      });
    }
function extraction(o) {
      return _.map(o, function (spec, field) {
        var fn = _.extract(spec, ['mutators', direction]) || _.identity;
        return [field, fn];
      });
    }
function extraction ( o ) { return _ . map ( o , function ( spec , field ) { var fn = _ . extract ( spec , [ 'mutators' , direction ] ) || _ . identity ; return [ field , fn ] ; } ) ; }
make a zipped array of field, mutator
make a zipped array of field mutator