fails to import calc operators, gaussian example + R func

from __future__ import print_function
from calc import calc
from calc import oper2
from calc import calcerr

class notebook(calc):
    def add_cust_func(self, func, key, num_args=1):
        self.operations_list[key]=operator(func,num_args=numargs)
def power(arg1,arg2):
    return arg2**arg1
def gaussian(x,u=0.0,std=1.0):
    import math
    return math.exp((x-u)/(2*std**2))/math.sqrt(2*math.pi*std**2)


print("calc")
calc1 =notebook()
calc.add_custom("operators.json")
calc.add_cust_func(power, '**',num_args=2)
calc.add_cust_func(gaussian, 'gauss',num_args=3)
calc.add_cust_func(r_func,'4th',num_args=1)

calc.print_oper()
while True:
    user = input("")
    if user == 'q':
        break
    try:
        calc.addto_q(user)
    except calcerr as Error:
        print('error', Error)
    calc.print_q()

calc
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-46-21026436a7f6> in <module>()
     16 print("calc")
     17 calc1 =notebook()
---> 18 calc.add_custom("operators.json")
     19 calc.add_cust_func(power, '**',num_args=2)
     20 calc.add_cust_func(gaussian, 'gauss',num_args=3)

TypeError: add_custom() missing 1 required positional argument: 'filename'