reshape tests
julia> A = Tensor(Dense(Sparse(Element(0))), LinearIndices((6, 6)))
6×6 Tensor{DenseLevel{Int64, SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, ElementLevel{0, Int64, Int64, Vector{Int64}}}}}:
 1   7  13  19  25  31
 2   8  14  20  26  32
 3   9  15  21  27  33
 4  10  16  22  28  34
 5  11  17  23  29  35
 6  12  18  24  30  36
julia> reshape(A, (3, 12))
3×12 Tensor{SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, ElementLevel{0, Int64, Int64, Vector{Int64}}}}}:
 1  4  7  10  13  16  19  22  25  28  31  34
 2  5  8  11  14  17  20  23  26  29  32  35
 3  6  9  12  15  18  21  24  27  30  33  36
julia> reshape(A, (3, 2, 6))
3×2×6 Tensor{DenseLevel{Int64, DenseLevel{Int64, SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, ElementLevel{0, Int64, Int64, Vector{Int64}}}}}}:
[:, :, 1] =
 1  4
 2  5
 3  6

[:, :, 2] =
 7  10
 8  11
 9  12

[:, :, 3] =
 13  16
 14  17
 15  18

[:, :, 4] =
 19  22
 20  23
 21  24

[:, :, 5] =
 25  28
 26  29
 27  30

[:, :, 6] =
 31  34
 32  35
 33  36
julia> reshape(A, (3, 2, 2, 3))
3×2×2×3 Tensor{DenseLevel{Int64, DenseLevel{Int64, SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, ElementLevel{0, Int64, Int64, Vector{Int64}}}}}}}:
[:, :, 1, 1] =
 1  4
 2  5
 3  6

[:, :, 2, 1] =
 7  10
 8  11
 9  12

[:, :, 1, 2] =
 13  16
 14  17
 15  18

[:, :, 2, 2] =
 19  22
 20  23
 21  24

[:, :, 1, 3] =
 25  28
 26  29
 27  30

[:, :, 2, 3] =
 31  34
 32  35
 33  36
julia> reshape(A, (9, 4))
9×4 Tensor{SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, ElementLevel{0, Int64, Int64, Vector{Int64}}}}}:
 1  10  19  28
 2  11  20  29
 3  12  21  30
 4  13  22  31
 5  14  23  32
 6  15  24  33
 7  16  25  34
 8  17  26  35
 9  18  27  36
julia> reshape(A, :)
36 Tensor{SparseDictLevel{Int64, Vector{Int64}, Vector{Int64}, Vector{Int64}, Dict{Tuple{Int64, Int64}, Int64}, Vector{Int64}, ElementLevel{0, Int64, Int64, Vector{Int64}}}}:
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
julia> A = Tensor(Dense(Element(0)), 1:36)
36 Tensor{DenseLevel{Int64, ElementLevel{0, Int64, Int64, Vector{Int64}}}}:
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
julia> reshape(A, (3, 12))
3×12 Tensor{DenseLevel{Int64, DenseLevel{Int64, ElementLevel{0, Int64, Int64, Vector{Int64}}}}}:
 1  4  7  10  13  16  19  22  25  28  31  34
 2  5  8  11  14  17  20  23  26  29  32  35
 3  6  9  12  15  18  21  24  27  30  33  36

