code: def should_bypass_proxies(url):
      
      get_proxy = lambda k: os.environ.get(k) or os.environ.get(k.upper())
  
      # First check whether no_proxy is defined. If it is, check that the URL
      # we're getting isn't in the no_proxy list.
      no_proxy = get_proxy('no_proxy')
      netloc = urlparse(url).netloc
  
      if no_proxy:
          # We need to check whether we match here. We need to see if we match
          # the end of the netloc, both with and without the port.
          no_proxy = no_proxy.replace(' ', '').split(',')
  
          ip = netloc.split(':')[0]
          if is_ipv4_address(ip):
              for proxy_ip in no_proxy:
                  if is_valid_cidr(proxy_ip):
                      if address_in_network(ip, proxy_ip):
                          return True
          else:
              for host in no_proxy:
                  if netloc.endswith(host) or netloc.split(':')[0].endswith(host):
                      # The URL does match something in no_proxy, so we don't want
                      # to apply the proxies on this URL.
                      return True
  
      # If the system proxy settings indicate that this URL should be bypassed,
      # don't proxy.
      # The proxy_bypass function is incredibly buggy on OS X in early versions
      # of Python 2.6, so allow this call to fail. Only catch the specific
      # exceptions we've seen, though: this call failing in other ways can reveal
      # legitimate problems.
      try:
          bypass = proxy_bypass(netloc)
      except (TypeError, socket.gaierror):
          bypass = False
  
      if bypass:
          return True
  
      return False
docs: Returns whether we should bypass proxies or not.