library(GO.db)
class(GO.db)
#[1] "GODb"
#attr(,"package")
#[1] "AnnotationDbi"
methods(class = "GODb")
 [1] $                      $<-                    annotatedDataFrameFrom assayData              assayData<-            coerce                
 [7] coerce<-               columns                combine                contents               dbconn                 dbfile                
[13] dbInfo                 dbmeta                 dbschema               ExpressionSet          featureNames           featureNames<-        
[19] initialize             isNA                   keys                   keytypes               mapIds                 mappedkeys            
[25] metadata               nhit                   revmap                 sample                 sampleNames            sampleNames<-         
[31] saveDb                 select                 show                   species                storageMode            storageMode<-         
[37] taxonomyId             updateObject          
see '?methods' for accessing help and source code
mapIds(GO.db,"GO:1904813","TERM","GOID")
'select()' returned 1:1 mapping between keys and columns
                    GO:1904813 
"ficolin-1-rich granule lumen"