Hi!
I want visualize data as a Gantt chart, i found some examples online with vega but i don't know why my piece of code does not work:
    {
  "$schema": "https://vega.github.io/schema/vega-lite/v3.json",
  "description": "Gantt chart",
  "data": {
    "name": "data",
    "url": {
      %context%: true
      %timefield%: @timestamp
      "index": "logstash-nemo.apps.webui-*",
      "body": {
        size:3000
        _source:[
          "@timestamp",
          "fields"
        ]
      }
    }
  }
  "transform": [
    {
      "type": "project",
      "fields": ["fields.Method"],
      "as": ["Method"]
    },
    {
      "type": "project",
      "fields": ["fields.startDate"],
      "as": ["startDate"]
    },
    {
      "type": "project",
      "fields": ["fields.endDate"],
      "as": ["endDate"]
    },
  ]
  "mark": "bar",
  "encoding": {
    "y": {"field": "_source.Method", "type": "ordinal"},
    "x": {"field": "_source.startDate", "type": "temporal"},
    "x2": {"field": "_source.endDate", "type": "temporal"}
  }
}
the error is:
Cannot read property 'startDate' of undefined
in addiction kibana rejects my transformations 
WARN Ignoring an invalid transform: {"as":["endDate"],"fields":["fields.endDate"],"type":"project"}.
Can you help me?