python missing 1 required positional argument 3a

1def your_method(self, arg1, arg2): # you must add the "self" argument in 1st position
2'''
3This kind of error happens when working with classes
4When you create methods for a class, you must always pass self as the first argument
5self designates the object in which it is called
6'''
7# for instance : 
8class Dog: # let create a class Dog
9  def __init__(self, color, age): # when you create a new Dog object, two parameters are required
10    self.color = color # here, whe use self to attach the attribute to this Dog object
11    self.age = age
12    self.bark("Woof")
13    
14  def bark(self, message): # your error might come from the fact you forgot to add the self element as the first argument in, at least, one method
15    print(message)
16    
17'''
18This is a very simple example but it stays true for every class
19You have to pass self as the first argument for each method
20'''

1Use json.dumps() instead. json.dump() needs a file object and dump JSON to it.