Created the crazy check.is_str_or_num_or_str_num_list() function.
Added the is_num() function and fixed the other number checking functions.
Missing imports.
Bug fix for the is_str_list() function.
Migrated the user function class to the new 'check' and 'base_class' modules.
Created the is_str_list() function.
Removed a dead import of num_types.
Created the RelaxNoneListNumError error class.
Added the is_num_list() function.
Fixed the capitalisation of the RelaxNoneListStrError error class.