Quick fix. New M => ME broke a custom MonthEnd subclass due to freqstr

and __hash__. Unsure if I'm just using things "incorrectly"

Author: dalejung

pandas/_libs/tslibs/period.pyx

@@ -2497,7 +2497,11 @@ cdef class _Period(PeriodMixin):
         >>> pd.Period('2020-01', 'D').freqstr
         'D'
         """
-        freqstr = freq_to_period_freqstr(self.freq.n, self.freq.name)
+        # I have a custom MonthEnd subclass that I need to be hash compatible with MonthEnd.
+        name = self.freq.name
+        if name == 'STC-M':
+            name = 'ME'
+        freqstr = freq_to_period_freqstr(self.freq.n, name)
         return freqstr
 
     def __repr__(self) -> str: