code: void removeVertexLabel(VertexLabel vertexLabel, boolean preserveData) {
          getTopology().lock();
          String fn = this.name + "." + VERTEX_PREFIX + vertexLabel.getName();
          if (!uncommittedRemovedVertexLabels.contains(fn)) {
              uncommittedRemovedVertexLabels.add(fn);
              TopologyManager.removeVertexLabel(this.sqlgGraph, vertexLabel);
              for (EdgeRole er : vertexLabel.getOutEdgeRoles().values()) {
                  er.remove(preserveData);
              }
              for (EdgeRole er : vertexLabel.getInEdgeRoles().values()) {
                  er.remove(preserveData);
              }
              if (!preserveData) {
                  vertexLabel.delete();
              }
              getTopology().fire(vertexLabel, "", TopologyChangeAction.DELETE);
          }
  
      }
docs: remove a given vertex label
  
  @param vertexLabel  the vertex label
  @param preserveData should we keep the SQL data