It is a dating system, which has no coincidences with the day, the time and the doctor. I need to go through all the appointments. I have done this but it does not work for me.

class centromedico_citas(models.Model):  
    _name = 'centromedico.citas'

    fconsulta = fields.Date(string="Fecha consulta", required=True)
    hconsulta = fields.Float(string="Hora consulta", required=True)
    cdoctores = fields.Many2one('centromedico.medicos', string="Doctor/a", ondelete="cascade")

    @api.depends('fconsulta', 'hconsulta', 'cdoctores')
    def _citaunica(self):
        for C in self:
            if C.hconsulta == self.hconsulta and C.fconsulta== self.fconsulta and C.cdoctores == self.cdoctores:               
                  raise exceptions.ValidationError("El doctor ya tiene una cita a esa hora ese día!")