def prerequisites(self):
        """
        Iterates through the inputs of the pipelinen and determines the
        all prerequisite pipelines
        """
        # Loop through the inputs to the pipeline and add the instancemethods
        # for the pipelines to generate each of the processed inputs
        prereqs = defaultdict(set)
        for input in self.inputs:  # @ReservedAssignment
            spec = self._study.spec(input)
            # Could be an input to the study or optional acquired spec
            if spec.is_spec and spec.derived:
                prereqs[spec.pipeline_getter].add(input.name)
        return prereqs
Iterates through the inputs of the pipelinen and determines the
        all prerequisite pipelines