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

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

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