Computed fields indicates many2one and one2many filed in selection filed . For example you can see below code in you .py file .

test = fields.Char(compute='_compute_upper',
                    inverse='_inverse_test',
                    search='_search_test')

@api.depends('name')
def _compute_test(self):
    for rec in self:
        rec. test = rec.name.test () if rec.name else False

def _inverse_test(self):
    for rec in self:
        rec.name = rec.test.lower() if rec. test else False

def _search_test(self, operator, value):
    if operator == 'like':
        operator = 'ilike'
    return [('name', operator, value)]

Note with the help of this code you can set your selection fileds and api.