code: def satisfiesExternal(cntxt: Context, n: Node, se: ShExJ.ShapeExternal, c: DebugContext) -> bool:
      
      if c.debug:
          print(f"id: {se.id}")
      extern_shape = cntxt.external_shape_for(se.id)
      if extern_shape:
          return satisfies(cntxt, n, extern_shape)
      cntxt.fail_reason = f"{se.id}: Shape is not in Schema"
      return False
docs: Se is a ShapeExternal and implementation-specific mechansims not defined in this specification indicate
       success.