How can I parse a `UnitfulQuantity` to return a unit describing only the `Time` dimension?

General Usage
,
1

I have a function where I want to parse a Unitful.Quantity argument provided by the user for only the Time dimensioned unit. For example…

f(1u"km/s") # should return u"s"
f(1u"km/d") # should return u"d"

Is this supported? I have some parameters crimes below that get me close, but the retuned value is of type Unitful.Unit{:Second, 𝐓}, not Unitful.FreeUnits{(s,), 𝐓, nothing}.

julia> using Unitful
julia> function crime(vel::Unitful.Velocity)
  # Flip the units so `Time` is in the numerator
  TL = inv(unit(vel))

 # Now we need to find which index (1 or 2) contains the Time unit
 timeaxis = findfirst(T -> T isa Unitful.Dimension{:Time}, collect(typeof(typeof(TL).parameters[2]).parameters[1]))

 # Now that we have the proper index, let's select the time unit
 timeunit = typeof(TL).parameters[1][timeaxis]
end

julia> crime(1u"m/s") |> typeof
Unitful.Unit{:Second, 𝐓}

julia> u"m" / crime(1u"m/s")
ERROR: MethodError: no method matching /(::Unitful.FreeUnits{(m,), 𝐋, nothing}, ::Unitful.Unit{:Second, 𝐓})
Closest candidates are:
  /(::Unitful.Units, ::Union{Dates.Day, Dates.Hour, Dates.Microsecond, Dates.Millisecond, Dates.Minute, Dates.Nanosecond, Dates.Second, Dates.Week}) at /Users/joey/.julia/packages/Unitful/PcVKX/src/dates.jl:91
  /(::Unitful.Units, ::Unitful.MixedUnits) at /Users/joey/.julia/packages/Unitful/PcVKX/src/logarithm.jl:111
  /(::Unitful.Units, ::Unitful.AbstractQuantity) at /Users/joey/.julia/packages/Unitful/PcVKX/src/quantities.jl:51
  ...
Stacktrace:
 [1] top-level scope
   @ REPL[10]:1

julia>
2

Alright I think I’ve figured out one way to do this.

julia> out = crime(1u"m/s")
julia> Unitful.FreeUnits{(out,), Unitful.𝐓}() == u"s"
true