Demonstrate error from operator== usage for SystematicVariation

sys_equality_error.py

#!/usr/bin/env python

from ROOT import gROOT
gROOT.SetBatch()
from ROOT import gSystem
gSystem.Load('libPATInterfaces.so')
from ROOT import CP
from ROOT.CP import SystematicVariation

# Get the equality operator
eq = getattr(CP, 'operator==')

# Custom comparison works
#def comp_systs(self, other):
#    return eq(self, other)
#SystematicVariation.__eq__ = comp_systs

# Setting operator directly gives error
SystematicVariation.__eq__ = eq

# Two "equal" objects
s1 = SystematicVariation('sys', 1)
s2 = SystematicVariation('sys', 1)

print 's1 == s2:', s1 == s2

Error message:

Traceback (most recent call last):
  File "./sys_equality_error.py", line 25, in <module>
    print 's1 == s2:', s1 == s2
TypeError: none of the 2 overloaded methods succeeded. Full details:
  static bool CP::operator==(const CP::SystematicVariation& a, const CP::SystematicVariation& b) =>
    takes at least 2 arguments (1 given)
  static bool CP::operator==(const CP::SystematicSet& a, const CP::SystematicSet& b) =>
    takes at least 2 arguments (1 given)