JuliaObject converts an R object to julia object
and returns a reference of the corresponding julia object.
JuliaObject(x)an environment of class JuliaObject, which contains an id corresponding to the actual julia object.
if (identical(Sys.getenv("AUTO_JULIA_INSTALL"), "true")) { ## julia_setup is quite time consuming
## doing initialization and automatic installation of Julia if necessary
julia_setup(installJulia = TRUE)
a <- JuliaObject(1)
}