Trying to export entire image collection but batch is not working?

Question

I am trying to download time series ET. But the batch tool is not working. Error:

In users/fitoprincipe/geetools:batch
Line 133: collection.size is not a function

var batch = require('users/fitoprincipe/geetools:batch');
var extent = ee.FeatureCollection("users/waqas50125012/KPK");
var StartDate = '2010-01-01';
var EndDate = '2010-12-31';
var dataset = ee.ImageCollection('MODIS/006/MOD16A2').select('ET').filterDate(StartDate,EndDate);
function clp(img) {
  return img.clip(extent);
}

var clip = dataset.map(clp);
var ET = clip.select('ET');
Map.centerObject(extent);
var evapotranspirationVis = {
  min: 0.0,
  max: 300.0,
  palette: [
    'ffffff', 'fcd163', '99b718', '66a000', '3e8601', '207401', '056201',
    '004c00', '011301'
  ],
};
Map.addLayer(ET, evapotranspirationVis, 'ET');
Map.addLayer(extent);
batch.Download.ImageCollection.toDrive({
  image: ET.select('ET'),
  description: 'ET',
  scale: 30,
  region: extent,
  maxPixels: 1e13,
});
var plotET = ui.Chart.image.series(ET.select('ET'), extent)
            .setOptions({
                title: 'ET short-term time series',
                hAxis: {title: 'Date'},
                vAxis: {title: 'ET'}
});

// Display.
print(plotET);

Answer 1

You're passing incorrect arguments to batch.Download.ImageCollection.toDrive. The first argument needs to be the ee.ImageCollection; you're providing a JavaScript object literal. The function tries to call ee.ImageCollection.size on something that is not an ee.ImageCollection. The export should be more like this:

var ops = {
  scale: 30,
  region: an_extent,
  maxPixels: 1e13,
}

batch.Download.ImageCollection.toDrive(col, 'folder_name', ops)