from . import STLWriter
def getMetaData():
    return {
        'type': 'mesh_writer',
        'plugin': {
            "name": "STL Writer"
        },
        'mesh_writer': {
            'extension': 'stl',
            'description': 'STL File'
        }
    }

def register(app):
    return STLWriter.STLWriter()

from . import STLWriter
def getMetaData():
    return {
        'type': 'mesh_writer',
        'plugin': {
            "name": "STL Writer"
        }
    }

def register(app):
    return STLWriter.STLWriter()

--- 
+++ 
@@ -4,6 +4,10 @@
         'type': 'mesh_writer',
         'plugin': {
             "name": "STL Writer"
+        },
+        'mesh_writer': {
+            'extension': 'stl',
+            'description': 'STL File'
         }
     }
 
Add writer metadata to the STL writer plugin so it can be used in Cura
