[BUG] Four-wire network with shunt has 5-termial and length-5 vectors in bus data

[hei06j]

In the four-wire network data, when there is a grounding/shunt in the network, the buses with shunt have 5 terminals and length-5 vectors. Given than the grounding is already represented in shunts, the 5-length vectors could potentially be reduced to length 4.

Given the dss file attached, with the code below

using PowerModelsDistribution
file = "Master.dss"

eng4w = parse_file(file, transformations=[transform_loops!])
eng4w["settings"]["sbase_default"] = 1              # Change power base here
eng4w["voltage_source"]["source"]["rs"] *= 0  # remove voltage source internal impedance
eng4w["voltage_source"]["source"]["xs"] *= 0  # remove voltage source internal impedance

math4w = transform_data_model(eng4w, kron_reduce=false, phase_project=false)
math4w["bus"]["1"]
math4w["bus"]["2"]

Master.dss.zip

As can be seen in the data for the two buses below, bus 1 has 5 terminals and length-5 vectors, whereas bus 2 has 4 terminals and length-4 vectors.

Dict{String, Any} with 12 entries:
  "vm_pair_lb" => Tuple{Any, Any, Real}[]
  "grounded"   => Bool[0, 0, 0, 0, 1]
  "vm_pair_ub" => Tuple{Any, Any, Real}[]
  "bus_i"      => 1
  "name"       => "1"
  "bus_type"   => 1
  "terminals"  => [1, 2, 3, 4, 5]
  "vmax"       => [Inf, Inf, Inf, Inf, Inf]
  "vbase"      => 0.240178
  "source_id"  => "bus.1"
  "vmin"       => [0.0, 0.0, 0.0, 0.0, 0.0]
  "index"      => 1

Dict{String, Any} with 14 entries:
  "vm_pair_lb" => Tuple{Any, Any, Real}[]
  "grounded"   => Bool[0, 0, 0, 1]
  "vm_pair_ub" => Tuple{Any, Any, Real}[]
  "bus_i"      => 2
  "name"       => "sourcebus"
  "bus_type"   => 3
  "terminals"  => [1, 2, 3, 4]
  "vmax"       => [1.0, 1.0, 1.0, 0.0, Inf]
  "vbase"      => 0.240178
  "source_id"  => "bus.sourcebus"
  "vmin"       => [1.0, 1.0, 1.0, 0.0, 0.0]
  "index"      => 2
  "va"         => [0.0, -2.0944, 2.0944, 0.0, 0.0]
  "vm"         => [1.0, 1.0, 1.0, 0.0, 0.0]