def copy(self, deep=False):
'''Make a shallow or deep copy of this instance.
@kwarg deep: If C{True} make a deep, otherwise
a shallow copy (C{bool}).
@return: The copy (C{This class} or subclass thereof).
'''
return _xcopy(self, deep=deep)
def fcopy(self, deep=False):
'''Copy this instance, C{shallow} or B{C{deep}}.
@return: The copy, a new instance (L{Fsum}).
'''
f = _xcopy(self, deep=deep)
# f._fsum2_ = self._fsum2_
# f._n = self._n
f._ps = list(self._ps) # separate copy
return f