I got this error:

```
syntax: missing condition in "elseif" at none:13
```

for this code, what the mistake I made?

```
function triple_exponential_smoothing(series, slen, α, β, γ, n_preds)
seasonals = initial_seasonal_components(series, slen)
println("The seasonalities are: $seasonals")
result = []
smooth = 0.0
trend = 0.0
for i in (0:length(series) + n_preds)
if i == 0 # iniial value
smooth = series[1]
trend = initial_trend(series, slen)
println!("The initial_trend is: $trend")
push!(result, series[1])
elseif
i >= length(series) # we are forecasting
m = i - series.len() + 1
push!(result, (smooth + m * trend) + seasonals[i % slen])
else # we are simulating history
val = series[i]
last_smooth = smooth
smooth = α * (val - seasonals[i % slen]) +
(1.0 - α)*(smooth + trend)
trend = β * (smooth - last_smooth) + (1.0 - β) * trend
seasonals[i % slen] = γ * (val - smooth) +
(1.0 - γ) * seasonals[i % slen]
push!(result, smooth + trend + seasonals[i % slen])
end
end
end
```