parameters: (cls, arg)
return_statement: return cls._netmask_cache[arg]
docstring: Make a (netmask, prefix_len) tuple from the given argument.
  
          Argument can be:
          - an integer (the prefix length)
          - a string representing the prefix length (e.g. "24")
          - a string representing the prefix netmask (e.g. "255.255.255.0")
docstring_summary: Make a (netmask, prefix_len) tuple from the given argument.
docstring_tokens: Make a ( netmask prefix_len ) tuple from the given argument .
function: def _make_netmask(cls, arg):
          """Make a (netmask, prefix_len) tuple from the given argument.
  
          Argument can be:
          - an integer (the prefix length)
          - a string representing the prefix length (e.g. "24")
          - a string representing the prefix netmask (e.g. "255.255.255.0")
          """
          if arg not in cls._netmask_cache:
              if isinstance(arg, _compat_int_types):
                  prefixlen = arg
              else:
                  try:
                      # Check for a netmask in prefix length form
                      prefixlen = cls._prefix_from_prefix_string(arg)
                  except NetmaskValueError:
                      # Check for a netmask or hostmask in dotted-quad form.
                      # This may raise NetmaskValueError.
                      prefixlen = cls._prefix_from_ip_string(arg)
              netmask = IPv4Address(cls._ip_int_from_prefix(prefixlen))
              cls._netmask_cache[arg] = netmask, prefixlen
          return cls._netmask_cache[arg]
function_tokens: def _make_netmask ( cls , arg ) : if arg not in cls . _netmask_cache : if isinstance ( arg , _compat_int_types ) : prefixlen = arg else : try : # Check for a netmask in prefix length form prefixlen = cls . _prefix_from_prefix_string ( arg ) except NetmaskValueError : # Check for a netmask or hostmask in dotted-quad form. # This may raise NetmaskValueError. prefixlen = cls . _prefix_from_ip_string ( arg ) netmask = IPv4Address ( cls . _ip_int_from_prefix ( prefixlen ) ) cls . _netmask_cache [ arg ] = netmask , prefixlen return cls . _netmask_cache [ arg ]