error fix in SelectNetworkGenes

    stop(paste0("Invalid selection gene_select: ", gene_select, '. Valid gene_selects are variable, fraction, all, or custom.'))

  }

  # handle different selection strategies

  if(gene_select == "fraction"){

    print('here1')

    # binarize counts matrix in chunks to save memory

    expr_mat <- GetAssayData(seurat_obj, slot='counts')

    chunks <- cut(1:nrow(expr_mat), n_chunks)

    expr_mat <- do.call(rbind, lapply(levels(chunks), function(x){

      print(x)

      cur <- expr_mat[chunks == x,]

      cur[cur > 0] <- 1

      cur

    }))

    print('here')

  #  print('size')

    #print(dim(expr_mat))

    group_gene_list <- list()

    if(!is.null(group.by)){

      # identify genes that are expressed in at least some fraction of cells

      gene_filter <- rowSums(expr_mat) >= round(fraction*ncol(seurat_obj));

      gene_list <- rownames(seurat_obj)[gene_filter]

      print('here')

    }

  } else if(gene_select == "variable"){

  # set the active WGCNA group, this is used for actually

  # making the co-expression network

  # TODO: I never actually use WGCNAGroup anywhere??

  if(is.null(group)){

    seurat_obj <- SetWGCNAGroup(seurat_obj, group='all', wgcna_name)

  } else{