search domain not seeing new fields

[fda-odoo]

class ResUsers(models.Model):
    _inherit = 'res.users'

    my_test = fields.Boolean()

    @api.model
    def a_function(self, emails):
        self.search([('my_test', '=', true)])

this code is generating a diagnostic 'my_test' is not a valid field in the search domain

[fda-odoo]

This issue is fixed by adding
from odoo import fields
fields being not defined, my_test is not detected as a valid field, so search domain can't find the field.