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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_subs_dict(self, qnodes=None):
 """ Return substitution dict for replacements into the template Subclasses may want to customize this method. """

        #d = self.qparams.copy()
        d = self.qparams
        d.update(self.optimize_params(qnodes=qnodes))
        # clean null values
        subs_dict = {k: v for k, v in d.items() if v is not None}
        #print("subs_dict:", subs_dict)
        return subs_dict