let setup_environment   ?(custom_channels = [])   ?(base_packages = [])   ?(banned_packages = [])   ?(main_subdir = "conda_dir")   ?(envs_subdir = "envs")   ?(python_version = `Python2)   install_path   name =   let channels = [ "bioconda"; "r" ] @ custom_channels in   {name; python_version; channels; base_packages; banned_packages; install_path; main_subdir; envs_subdir}