code: def _create_patterns(self, properties=None):
          
          return [self.pattern_type(**self.pattern_parameters)
                  for i in range(self.patterns_per_label)]
docs: Return a list (of length patterns_per_label) of
          PatternGenerator instances.  Should use pattern_type and
          pattern_parameters to create each pattern.
  
          properties is a dictionary, e.g. {'pattern_label':
          pattern_label}, which can be used to create PatternGenerators
          depending on the requested pattern_label