def lai(params: dict, states: dict) -> float:
    """
    Calculates leaf area index

    Parameters
    ----------
    params: dict
        sla: float
            Specific leaf area. [m2 {leaf} mg-1 {CH2O}]
     states: dict
        CLeaf: float
            Carbohydrates stored in the leaves [mg m-2]

    Returns
    -------
    float
        LAI is a semi-state of the model. [m2 {leaf} m-2]

    """
    lai_ = params['sla'] * states['CLeaf']

    return lai_