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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 set_defaults(self):
 """ Set defaults for fields needed to write the header if they have defaults. Notes ----- - This is NOT called by `rdheader`. It is only automatically called by the gateway `wrsamp` for convenience. - This is also not called by `wrheader` since it is supposed to be an explicit function. - This is not responsible for initializing the attributes. That is done by the constructor. See also `set_p_features` and `set_d_features`. """

        rfields, sfields = self.get_write_fields()
        for f in rfields:
            self.set_default(f)
        for f in sfields:
            self.set_default(f)