code: def check_headers(headers):
      assert_(
          type(headers) is list,
          "Headers (%r) must be of type list: %r"
          % (headers, type(headers)),
      )
      for item in headers:
          assert_(
              type(item) is tuple,
              "Individual headers (%r) must be of type tuple: %r"
              % (item, type(item)),
          )
          assert_(len(item) == 2)
          name, value = item
          name = check_string_type(name, "Header name")
          value = check_string_type(value, "Header value")
          assert_(
              name.lower() != "status",
              "The Status header cannot be used; it conflicts with CGI "
              "script, and HTTP status is not given through headers "
              "(value: %r)." % value,
          )
          assert_(
              "\n" not in name and ":" not in name,
              "Header names may not contain ':' or '\\n': %r" % name,
          )
          assert_(header_re.search(name), "Bad header name: %r" % name)
          assert_(
              not name.endswith("-") and not name.endswith("_"),
              "Names may not end in '-' or '_': %r" % name,
          )
          if bad_header_value_re.search(value):
              assert_(
                  0,
                  "Bad header value: %r (bad char: %r)"
                  % (value, bad_header_value_re.search(value).group(0)),
              )
  
imports: import re
  import sys
  import warnings
label_desc: Use image node_id 8 for calling a global function with example usage: check_headers(headers) without return types