R语言问题大家看看请解答下

gene.df<-bitr(gene, fromType = "ENSEMBL",

• toType = c("SYMBOL","ENTREZID"),
• OrgDb = org.Mm.eg.db)
  Error in .testForValidKeys(x, keys, keytype, fks) :
  None of the keys entered are valid keys for 'ENSEMBL'. Please use the keys method to see a listing of valid arguments.