How to let the user add 'None' to an specific array in a dictionary?

[noahverner1995]

if None in the_dictionary_list[key_entrada]:
    print("None is already in the list")
else:
    the_dictionary_list[key_entrada].insert(0, 'None')

Thank you again! Once more, I will update the final version of this program, now the user can choose whether adding a 'None' value to the arrays of one of the available keys only once, or not adding anything at all :

def existe(key, value, diccionario):
    return key in diccionario and value in diccionario[key]

entrada = input('All right, do you want to add a "None" item to an array in the dictionary? (y/n):')

while True:
    
    if entrada == 'y':
        key_entrada = input('Cool, now tell me at which key do you want me to add a "None" item? Type only a valid key name:')
        while True:            
            if key_entrada in the_dictionary_list:
                if existe(key_entrada, 'None', the_dictionary_list) == False:
                    the_dictionary_list[key_entrada].insert(0, 'None')
                    print('\u001b[43mthe_dictionary_list IS UPDATED:\033[0m')
                    print(the_dictionary_list)
                    print('\n')
                    key_entrada = input('Done, do you want to add another one? (y/n):')
                    if key_entrada == 'n':
                        entrada = 'n'
                        break
                    if key_entrada == 'y':
                        key_entrada = input('Cool, now tell me at which key do you want me to add a "None" item? Type only a valid key name:')
                    else:
                        key_entrada = input("Invalid Input, Type 'y' or 'n' without single quotation marks:")
                        while True:
                            if key_entrada == 'n':
                                entrada = 'n'
                                break
                            if key_entrada == 'y':
                                key_entrada = input('Cool, now tell me at which key do you want me to add a "None" item? Type only a valid key name:')
                                break
                            elif key_entrada != 'n' or key_entrada != 'y':
                                key_entrada = input("Invalid Input, Type 'y' or 'n' without single quotation marks:")
                                
                if existe(key_entrada, 'None', the_dictionary_list) == True:
                    key_entrada = input('That input DOES ALREADY EXIST in the dictionary, try again with another key name:') 
            
            elif entrada == 'n':
                break
            
            else:
                key_entrada = input('That input does not exist in the dictionary, try again, Type only a valid key name:')               
                                   
    if entrada == 'n':
        break  
    
    elif entrada != 'y' or entrada != 'n':
        entrada = input("Invalid Input, Type 'y' or 'n' without single quotation marks:")