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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_rc_strings(cls):
 """ Recursive method to get the base strings in the rcParams dictionary. This method takes the :attr:`_rcparams_string` attribute from the given `class` and combines it with the :attr:`_rcparams_string` attributes from the base classes. The returned frozenset can be used as base strings for the :meth:`psyplot.config.rcsetup.RcParams.find_and_replace` method. Returns ------- list The first entry is the :attr:`_rcparams_string` of this class, the following the :attr:`_rcparams_string` attributes of the base classes according to the method resolution order of this class"""

        return list(unique_everseen(chain(
            *map(lambda base: getattr(base, '_rcparams_string', []),
                 cls.__mro__))))