fme and arcpy - calling arcpy functions, where?

I tr to execute the following arcpy function from a fme workbench:

 

 

arcpy.CalculatePolygonMainAngle_cartography("FeatureLayer", "poly_angle")

 

 

from the PythonCaller transformer to calculate a polygons main angle. What I can't really understand (as my python skills are absolute nonexisting) is how to wrap than inside the template function interface. I have tried to integrate the arcpy- function like this:

 

 

---

 

import fmeobjects

 

import arcpy

 

 

def angleFeature(feature):

 

    ang = arcpy.CalculatePolygonMainAngle_cartography("FeatureLayer", "angle")

 

    feature.setAttribute("angle", ang)

 

--

 

 

but when trying to run the workbench I get the following error

 

 

ERROR 000732: Input Features: Dataset FeatureLayer does not exist or is not supported

 

 

so Im stuck with the problem that the function cant find my source (wich is a Geodatabase_SDE reader. It also feels that once I get the features into the function, CalculatePolygonMainAngle will write the angle to the attribute "angle" and then fme will write it once again in feature.setAttribute.

 

 

I obviously dont know much python, perhaps someone else knows and might help out?