Error while running learn_graph(cds, use_partition = FALSE)

[Fatemeh99m]

I am using version 5 seurat and CCAIntegration as the integration method for my data set. after creating cds, I have problems while running learn graph. I faced this error : Error: names(cds@clusters[[reduction_method]]$partitions) == NULL
I didnt run "cds <- cluster_cells(cds)" cause I wanted to use cca_clusters.
This is my code :
`gene_annotation <- as.data.frame(rownames(obj@reductions[["pca"]]@feature.loadings), row.names = rownames(obj@reductions[["pca"]]@feature.loadings))
colnames(gene_annotation) <- "gene_short_name"
head(gene_annotation)

cell_metadata <- as.data.frame(obj[["RNA"]]$counts@Dimnames[[2]], row.names = obj[["RNA"]]$counts@Dimnames[[2]])
colnames(cell_metadata) <- "barcode"
head(cell_metadata)

New_matrix <- obj[["RNA"]]$data
New_matrix <- New_matrix[rownames(obj@reductions[["pca"]]@feature.loadings), ]
expression_matrix <- New_matrix

cds<- new_cell_data_set(expression_matrix,
cell_metadata = cell_metadata,
gene_metadata = gene_annotation)

list_cluster <-Idents(obj)
names(list_cluster) <- obj[["RNA"]]$data@Dimnames[[2]]
cds@clusters@listData[["UMAP"]][["clusters"]] <- list_cluster

cds@clusters@listData[["UMAP"]][["louvain_res"]] <- "NA"
cds@int_colData@listData$reducedDims$UMAP <-obj@reductions[["umap.cca"]]@cell.embeddings

cds <- preprocess_cds(cds, num_dim = 35)
cds <- align_cds(cds)
cds <- learn_graph(cds, verbose = FALSE, use_partition = FALSE)`