I need to check that within my 'appointment' model does not coincide the time, the doctor and the day. That is, the 'appointments' do not coincide. I have done this but it does not work for me. Would someone know how to do it?

class centromedico_appointments(models.Model):

    _name = 'centromedico.appointments'

    datea = fields.Date(string="Fecha consulta", required=True)

   timea = fields.Float(string="Hora consulta", required=True)

   doctora = fields.Many2one('centromedico.medicos', string="Doctor/a", required=True, ondelete="cascade")

    @api.depends('fconsulta', 'hconsulta', 'cdoctores')

    def _uniqueappointment(self):

        for C in self:

            if C.datea  == centromedico.datea and C.timea == centromedico.timea and C.doctora == centromedico.doctora: 

                raise exceptions.ValidationError("This doctor already has an appointment at that time that day")