as.character.file       Convert file connections to strings
assert_all_are_dirs     Is the path a directory? Checks to see if the
                        input path is a directory.
assert_all_are_empty_files
                        Is a file too big or small?
assert_all_are_executable_files
                        Is the file accessible?
assert_all_are_existing_files
                        Does the file exist?
assert_all_are_libraries
                        Is the directory a known R library?
assert_is_bzfile_connection
                        Is the input a connection?
