Loads symbol from json string.

    Parameters
    ----------
    json_str : str
        A JSON string.

    Returns
    -------
    sym : Symbol
        The loaded symbol.

    See Also
    --------
    Symbol.tojson : Used to save symbol into json string.

def load_json(json_str):
    """Loads symbol from json string.

    Parameters
    ----------
    json_str : str
        A JSON string.

    Returns
    -------
    sym : Symbol
        The loaded symbol.

    See Also
    --------
    Symbol.tojson : Used to save symbol into json string.
    """
    if not isinstance(json_str, string_types):
        raise TypeError('fname required to be string')
    handle = SymbolHandle()
    check_call(_LIB.MXSymbolCreateFromJSON(c_str(json_str), ctypes.byref(handle)))
    return Symbol(handle)