bn.fit and cluster objects?

Question

I am having an issue get a bn.fit object to run; I have specified the nodes and arcs as follows:

nodes <- empty.graph(names(df))

arcs = matrix(c('A','B','A','C','A','D','A','E','A','F','A','G','A','H','A','I','A','J','A','K','A','L','A','M','A','N','A','O','A','P','A','Q','A','R','A','S','A','T','A','U','A','V','A','W','A','X','A','Y','A','Z','A','AA','A','AB','A','AC','A','AD','A','AE','A','AF','A','AG','A','AH','A','AI','A','AJ','A','AK','A','AL','A','AM','A','AN','A','AO','A','AP','A','AQ','A','AR','A','AS','A','AT','A','AU','A','AV','A','AW','A','AX','A','AY','A','AZ','A','BA','A','BB','A','BC','A','BD','A','BE','A','BF','A','BG','A','BH','A','BI','A','BJ','A','BK','A','BL','A','BM','A','BN','A','BO','A','BP','A','BQ','A','BR','A','BS','A','BT','A','BU','A','BV','A','BW','A','BX','A','BY','A','BZ','A','CA','A','CB','A','CC','A','CD','A','CE','A','CF','A','CG','A','CH','A','CI','A','CJ','A','CK','A','CL','A','CM','A','CN','A','CO','A','CP','A','CQ','A','CR','A','CS','A','CT','A','CU','A','CV','A','CW','A','CX','A','CY','A','CZ','A','DA','A','DB','A','DC','A','DD','A','DE','A','DF','A','DG','A','DH','A','DI','A','DJ','A','DK','A','DL','A','DM','A','DN','A','DO','A','DP','A','DQ','A','DR','A','DS','A','DT','A','DU','A','DV','A','DW','A','DX','A','DY','A','DZ','A','EA','A','EB','A','EC','A','ED','A','EE','A','EF','A','EG','A','EH','A','EI','A','EJ','A','EK','A','EL','A','EM','A','EN','A','EO','A','EP','A','EQ','A','ER','A','ES','A','ET','A','EU','A','EV','A','EW','A','EX','A','EY','A','EZ','A','FA','A','FB','A','FC','A','FD','A','FE','A','FF','A','FG','A','FH','A','FI','A','FJ','A','FK','A','FL','A','FM','A','FN','A','FO','A','FP','A','FQ','A','FR','A','FS','A','FT','A','FU','A','FV','A','FW','A','FX','A','FY','A','FZ','A','GA','A','GB','A','GC','A','GD','A','GE','A','GF','A','GG','A','GH','A','GI','A','GJ','A','GK','A','GL','A','GM','A','GN','A','GO','A','GP','A','GQ','A','GR','A','GS','A','GT','A','GU','A','GV','A','GW','A','GX','A','GY','A','GZ','A','HA','A','HB','A','HC','A','HD','A','HE','A','HF','A','HG','A','HH','A','HI','A','HJ'), ncol = 2, byrow = TRUE,dimnames = list(NULL, c("from", "to")))

So the eventual outlook I want is Node A's relationship with Node B, Node C and so on.

So I am using the following to construct the bn;

bn<-bn.fit(nodes,df,arcs)

It returns the following issue:

Error in check.cluster(cluster) : cluster is not a valid cluster object.

Herein I am lost; new to the bnlearn package so this maybe a major basic question but please help!