To write the partner manipulation methods, you need to perform the following steps:

1. Define a method called get_email_addresses():

    @api.model 
    def get_email_addresses(self, partner): 

2. Call mapped() to get the email addresses of the contacts of the partner:

    return partner.mapped('child_ids.email') 

3. Define a method called get_companies():

    @api.model 
    def get_companies(self, partners): 

4. Call mapped() to get the different companies of the partners:

    return partners.mapped('parent_id')