get_requirements doesn't work with constructors

@show_requirements SparseTabularPOMDP(pomdp)

fails with

MethodError: no method matching get_requirements(::Type{SparseTabularPOMDP}, ::Tuple{TigerPOMDP})
Closest candidates are:
get_requirements(!Matched::Function, ::Tuple) at /home/zach/.julia/packages/POMDPs/0djkf/src/requirements_interface.jl:26

Reproduce the @show_requirements SparseTabularPOMDP(pomdp) call and inspect the get_requirements interface, including requirements_interface.jl at the reported location. Trace how the constructor type and argument tuple are dispatched, then verify that the constructor case no longer raises the reported MethodError and produces the expected requirements output.

Written by the indexing model from the issue text.