ERROR: LoadError: UndefVarError: @formula not defined

[lauswullum]

Hi, Thanks for writing this package.

Potential bug

I found a potential bug, where @formula from StatsModels.jl is not automatically available
when only writing
using Survival
without
using StatsModels

MWE to reproduce the problem

using Survival
using StatsBase
using DataFrames
event = EventTime.(10 .+ randn(10), sample([true, false], 10))
coxph(@formula(events ~ x), DataFrame(x = randn(10), events = event))

output:

ERROR: LoadError: UndefVarError: @formula not defined

[ararslan]

Good catch. Not a bug per se but it would be a good improvement to re-export @formula from StatsModels. Should be as simple as adding @formula to the export list. This would also allow us to remove the dependency on StatsModels in the docs/ project.