code: def filterwarnings(action, message="", category=Warning, module="", lineno=0,
                     append=0):
      
      assert action in ("error", "ignore", "always", "default", "module",
                        "once"), "invalid action: %r" % (action,)
      assert isinstance(message, basestring), "message must be a string"
      assert isinstance(category, type), "category must be a class"
      assert issubclass(category, Warning), "category must be a Warning subclass"
      assert isinstance(module, basestring), "module must be a string"
      assert isinstance(lineno, int) and lineno >= 0, \
             "lineno must be an int >= 0"
      item = (action, re.compile(message, re.I), category,
              re.compile(module), lineno)
      if append:
          filters.append(item)
      else:
          filters.insert(0, item)
docs: Insert an entry into the list of warnings filters (at the front).
  
      'action' -- one of "error", "ignore", "always", "default", "module",
                  or "once"
      'message' -- a regex that the warning message must match
      'category' -- a class that the warning must be a subclass of
      'module' -- a regex that the module name must match
      'lineno' -- an integer line number, 0 matches all warnings
      'append' -- if true, append to the list of filters