Jena Fuseki GeoSPARQL: cannot delete data

Question

Trying to delete data from a Jena Fuseki server running the GeoSPARQL extension.

The queries don't seem to be effective.

The output from the server when trying either DELETE or DELETE DATA is:

23:29:06 WARN  Fuseki     :: [2] Parse error: Encountered " "delete" "DELETE "" at line 15, column 1.
23:29:52 WARN  Fuseki     :: [4] Parse error: Encountered " <DELETE_DATA> "DELETE DATA "" at line 15, column 1.

Command to run the server, from scratch without an empty index and tdb file:

java -jar jena-fuseki-geosparql-4.2.0.jar  \
  -rf file.n3 \
  --index_expiry 50000000000000,500000000000,500000000000 -p 3034 \
  -t ./geosparql-tdb2 \
  -t2 --update \
  --spatial_index ./geosparql-tdb2/spatial.index

(prefix spa: <http://jena.apache.org/spatial#>)

The delete query is thus:

DELETE DATA { ?feature a sosa:featureOfInterest . }
WHERE {
  ?feature a sosa:featureOfInterest ;
  spa:withinBox(54.3 -116.5 34.2 -93.9) .
}

Which corresponds to a select query which is working as expected (i.e. is correctly selecting the rows which should be deleted):

select * WHERE {
  ?feature spa:withinBox(54.3 -116.5 34.2 -93.9) .
}

Any ideas?

Edit: The delete query which was causing the parse error was incorrect. This new delete query doesn't cause an error. However, this still doesn't delete the data.

DELETE {
  ?g a geo:Geometry .
}
WHERE {
  ?g a geo:Geometry .
  ?g spa:withinBox(54.3 -116.5 34.2 -93.9) .
}

Also, the query URL is /ds/query and the delete URL is /ds/update.

Finally, the request is being performed in python as follows:

def run_sparql(s, qtype='query'):
  url = 'http://localhost:3034/ds/' + qtype
  payload = s
  headers = {'Content-Type': 'application/sparql-query'}
  res = requests.post(url, data=payload, headers=headers)

The response code for the delete query is 415 while for the select it is 200.

Edit #2: Changing the content type from application/sparql-query to application/sparql-update results in a status code of 400 and still does not delete the data as expected.

To be clear:

s = '''
prefix geo: <http://www.opengis.net/ont/geosparql#> 
prefix spa: <http://jena.apache.org/spatial#>
DELETE {
  ?g a geo:Geometry .
}
WHERE {
  ?g a geo:Geometry .
  ?g spa:withinBox(54.3 -116.5 34.2 -93.9) .
}
'''

url = 'http://localhost:3034/ds/update'
payload = s
headers = {'Content-Type': 'application/sparql-update'}
res = requests.post(url, data=payload, headers=headers)

Even this is not working:

prefix geo: <http://www.opengis.net/ont/geosparql#> 
DELETE {?g a geo:Geometry}