def get_feature_dna(self, ctx, ref, feature_id_list):
"""
Retrieve Feature DNA sequences.
@param feature_id_list List of Feature IDs for which to retrieve sequences.
If empty, returns data for all features.
@return Mapping of Feature IDs to their DNA sequence.
:param ref: instance of type "ObjectReference"
:param feature_id_list: instance of list of String
:returns: instance of mapping from String to String
"""
# ctx is the context object
# return variables are: returnVal
#BEGIN get_feature_dna
ga = GenomeAnnotationAPI_local(self.services, ctx['token'], ref)
returnVal = ga.get_feature_dna(feature_id_list)
#END get_feature_dna
# At some point might do deeper type checking...
if not isinstance(returnVal, dict):
raise ValueError('Method get_feature_dna return value ' +
'returnVal is not type dict as required.')
# return the results
return [returnVal]
