code: function(assemble, next) {
  
        grunt.verbose.writeln('Validating options');
  
        if (utils.endsWithDot(assemble.options.ext)) {
          grunt.warn('Invalid ext "' + assemble.options.ext + '". ext cannot end with a period.');
          done(false);
        }
  
        // find an engine to use
        assemble.options.engine = assemble.options.engine || 'handlebars';
        grunt.verbose.ok('>> Current engine:'.yellow, assemble.options.engine);
  
        assemble.engine.load(assemble.options.engine);
  
        var initializeEngine = function(engine, options) { engine.init(options, { grunt: grunt, assemble: assemble }); };
        assemble.options.initializeEngine = assemble.options.initializeEngine || initializeEngine;
  
        var registerFunctions = function(engine) { engine.registerFunctions(); };
        assemble.options.registerFunctions = assemble.options.registerFunctions || registerFunctions;
  
        var registerPartial = function(engine, filename, content) { engine.registerPartial(filename, content); };
        assemble.options.registerPartial = assemble.options.registerPartial || registerPartial;
  
        assemble.partials = file.expand(assemble.options.partials);
  
        if (_.isArray(assemble.options.dataFiles) && assemble.options.dataFiles.length > 0) {
          assemble.dataFiles = file.expand(assemble.options.dataFiles);
          //assemble.options.data = {};
        }
  
        // Expand layout into layoutFiles if a glob pattern is specified
        if (assemble.options.layouts) {
          assemble.layoutFiles = file.expand({filter: 'isFile'}, assemble.options.layouts);
        }
  
        if (assemble.layoutFiles && assemble.layoutFiles.length !== 0) {
          grunt.verbose.writeln('Found layout files:'.yellow, assemble.layoutFiles);
        } else {
          assemble.layoutFiles = null;
        }
  
        assemble.options.initializeEngine(assemble.engine, assemble.options);
        assemble.options.registerFunctions(assemble.engine);
  
        next(assemble);
      }
docs: functions for use in build steps