modify_validate.py

# First approach

class A:
    vadifier = None
    
    def create(self, ...):
        ...
        if self.vadifier:
		    self.vadifier.run(new_version)
        ...
       
class B(A):
    
    def __init__(self, vadifier_config):
        self.vadifier = SpecialVadifier(vadifier_config)
        
class C(A):
    
   def __init__(self, vadifier = None):
	   	self.vadifier = vadifier
        
class D(A):
	vadifier = NoCustomizationRequiredVadifier()    


# Second approach
      
class A:

    def create(self, ..., vadifier = None):
        ...
        if vadifier:
            vadifier.run(new_version)
        ...

class B(A):

    def create(self, ..., vadifier = None):
        ...
	    vadifier = vadifier or MyOwnVadifier()
        super(B).create(..., vadifier=vadifier)