Error when creating a chart via a batch request - google-sheets-api

Question

I'm trying to create a new chart, following the examples presented in Google sheets API. I'm getting the following error:
HttpError 400 when requesting
https://slides.googleapis.com/v1/presentations/PRESENTATION_ID:batchUpdate?alt=json
returned "Invalid JSON payload received. Unknown name "add_chart" at
'requests[0]': Cannot find field."
Has anyone encountered this before?
Other requests are working normal (replace text, add text, clone presentation, etc)
this request is being copied from the example in Google sheets API.
sourceSheetId is the id where I have the data for the chart saved in.
{
"addChart": {
"chart": {
"spec": {
"title": "Model Q1 Sales",
"basicChart": {
"chartType": "COLUMN",
"legendPosition": "BOTTOM_LEGEND",
"axis": [
{
"position": "BOTTOM_AXIS",
"title": "Model Numbers"
},
{
"position": "LEFT_AXIS",
"title": "Sales"
}
],
"domains": [
{
"domain": {
"sourceRange": {
"sources": [
{
"sheetId": sourceSheetId,
"startRowIndex": 0,
"endRowIndex": 7,
"startColumnIndex": 0,
"endColumnIndex": 1
}
]
}
}
}
],
"series": [
{
"series": {
"sourceRange": {
"sources": [
{
"sheetId": sourceSheetId,
"startRowIndex": 0,
"endRowIndex": 7,
"startColumnIndex": 1,
"endColumnIndex": 2
}
]
}
},
"targetAxis": "LEFT_AXIS"
},
{
"series": {
"sourceRange": {
"sources": [
{
"sheetId": sourceSheetId,
"startRowIndex": 0,
"endRowIndex": 7,
"startColumnIndex": 2,
"endColumnIndex": 3
}
]
}
},
"targetAxis": "LEFT_AXIS"
},
{
"series": {
"sourceRange": {
"sources": [
{
"sheetId": sourceSheetId,
"startRowIndex": 0,
"endRowIndex": 7,
"startColumnIndex": 3,
"endColumnIndex": 4
}
]
}
},
"targetAxis": "LEFT_AXIS"
}
],
"headerCount": 1
}
},
"position": {
"newSheet": True
}
}
}
}
I was expecting the chart to be created and receive a response with chartId, however I'm getting from the request a 400 status:
HttpError 400 when requesting
https://slides.googleapis.com/v1/presentations/PRESENTATION_ID:batchUpdate?alt=json
returned "Invalid JSON payload received. Unknown name "add_chart" at
'requests[0]': Cannot find field."