A fillet is a curved surface of a constant or variable radius that is tangent to, and that joins two surfaces. Together, these three surfaces form either an inside corner or an outside corner.
To specify a fillet within your script, you must have a part open, then:
Create a Fillet by using the isa keyword.
Fillet1 isa ConstantEdgeFillet ( )
Right-click anywhere inside the parentheses and select Get Edge or Get Surface. Then, in the geometry area, select the edge or the face to be filleted.