class_docstr: WSGI middleware validating security on response.
  
  It validates:
  - responses have Content-Type
  - responses have X-Content-Type-Options: nosniff
  - text/html responses have CSP header. It also validates whether the CSP
    headers pass basic requirement. e.g., default-src should be present, cannot
    use "*" directive, and others. For more complete list, please refer to
    _validate_csp_policies.
  
  Instances of this class are WSGI applications (see PEP 3333).
code: def _validate_x_content_type_options(self, headers):
      option = headers.get("X-Content-Type-Options")
      if option == "nosniff":
          return
  
      _maybe_raise_value_error(
          'X-Content-Type-Options is required to be "nosniff"'
      )
  
file_path: tensorboard/tensorboard/backend/security_validator.py
imports: import dataclasses
  from typing import Collection
  from werkzeug.datastructures import Headers
  from werkzeug import http
  from tensorboard.util import tb_logging
label_desc: Use image node_id 5 for calling the SecurityValidatorMiddleware obj's underlying member method code with example usage: obj._validate_x_content_type_options(headers) without return types