Sparse indexing fails when keys not unique

[cdeterman]

I have a table like the following

2-d NDSparse with 10 values (2 field named tuples):
A B │ C data
───────────┼───────────
"a1" "b3" │ "c1" 2
"a2" "b1" │ "c1" 2
"a3" "b2" │ "c3" 4
"a3" "b2" │ "c2" 3

I would like to index the table like the following

mytable["a1","b3"]

Which works fine, however, when I try to index on one of the keys pairs that is not unique I get the following error. Have I missed something, is this not allowed for non-unique keys, or is this a bug?

mytable["a3","b2"]

ERROR: KeyError: key ("a3", "b2") not found
Stacktrace:
[1] _getindex_scalar(::IndexedTables.NDSparse{NamedTuples._NT_T_data{String,Int64},Tuple{String,String},IndexedTables.Columns{Name
dTuples._NT_R_S{String,String},NamedTuples._NT_R_S{PooledArrays.PooledArray{String,UInt8,1,Array{UInt8,1}},PooledArrays.PooledArray
{String,UInt8,1,Array{UInt8,1}}}},IndexedTables.Columns{NamedTuples._NT_T_data{String,Int64},NamedTuples._NT_T_data{PooledArrays.Po
oledArray{String,UInt8,1,Array{UInt8,1}},Array{Int64,1}}}}, ::Tuple{String,String}) at C:\Users\y66534.julia\v0.6\IndexedTables\sr
c\indexing.jl:10
[2] getindex(::IndexedTables.NDSparse{NamedTuples._NT_T_data{String,Int64},Tuple{String,String},IndexedTables.Columns{NamedTuples.
_NT_R_S{String,String},NamedTuples._NT_R_S{PooledArrays.PooledArray{String,UInt8,1,Array{UInt8,1}},PooledArrays.PooledArray{String,
UInt8,1,Array{UInt8,1}}}},IndexedTables.Columns{NamedTuples._NT_T_data{String,Int64},NamedTuples._NT_T_data{PooledArrays.PooledArra
y{String,UInt8,1,Array{UInt8,1}},Array{Int64,1}}}}, ::String, ::String) at C:\Users\userid.julia\v0.6\IndexedTables\src\indexing.j
l:3
[3] eval(::Module, ::Any) at .\boot.jl:235
[4] eval(::Any) at .\boot.jl:234
[5] macro expansion at C:\Users\userid.julia\v0.6\Atom\src\repl.jl:118 [inlined]
[6] anonymous at .<missing>:?