Check type of space in Symmetrizing operator

nifty5/operators/symmetrizing_operator.py

@@ -17,16 +17,19 @@
 # and financially supported by the Studienstiftung des deutschen Volkes.
 
 from __future__ import absolute_import, division, print_function
+
+from .. import dobj
 from ..compat import *
 from ..domain_tuple import DomainTuple
+from ..domains.rg_space import RGSpace
 from ..field import Field
 from .endomorphic_operator import EndomorphicOperator
-from .. import dobj
 
 
-# MR FIXME: we should make sure that the domain is a harmonic RGSpace, correct?
 class SymmetrizingOperator(EndomorphicOperator):
     def __init__(self, domain):
+        if not (isinstance(domain, RGSpace) and domain.harmonic):
+            raise TypeError
         self._domain = DomainTuple.make(domain)
         self._ndim = len(self.domain.shape)