implement a function to choose the corresponding lexer
create a class to concretize files
create a class for concretizing crds
create a class for concretizing code fragments
[bug fix] wrong type argument
create a class to concretize blocks
create a class for concretizing links of code fragments
create a class for concretizing genealogies of code fragments
create a class for concretizing clone sets
create a class for concretizing clone set lnks
create a class for concretizing clone genealogies