Internal function to check that a time series list is a list of zoo objects and has a minimum number of objects. For a more comprehensive test, use tsl_diagnose().
utils_check_args_tsl(tsl =NULL, min_length =2)
Arguments
tsl: (required, list) list of zoo objects. Default: NULL
min_length: (required, positive integer) minimum number of zoo objects in tsl. Default: 2