import dill
import lmfit
from collections import OrderedDict as od


#%% 1) this works ####################################
class test(object):

    def inside_func(*args):
        return

    def __init__(self):
        # check OrderedDict dill-pickleable (should be)
        self.d = od([])
        self.d.update({'func': self.inside_func})
        return

t = test()

with open('test.pkl', 'wb') as f:
    dill.dump(t, f)


#%% 2) this also works ###############################

def outside_func(*args):
    return

class test(object):

    def __init__(self):
        # some dummy Parameters set
        self.p = lmfit.Parameters()
        self.p.add('var1')
        self.p.add('var2')

        # addition of 'func' to _asteval's symtable from outside class scope
        self.p._asteval.symtable['func'] = outside_func
        return

t = test()

with open('test.pkl', 'wb') as f:
    dill.dump(t, f)



#%% 3) this doesn't work ###############################

class test(object):
    def inside_func(*args):
        return

    def __init__(self):
        # some dummy Parmaeters set
        self.p = lmfit.Parameters()
        self.p.add('var1')
        self.p.add('var2')

        # addition of 'func' to _asteval's symtable from inside class scope
        if not any('func' == x for x in self.p._asteval.symtable.keys()):
            self.p._asteval.symtable.update({'func': self.inside_func})
        return

t = test()

with open('test.pkl', 'wb') as f:
    dill.dump(t, f)