code: def metapolicy(self, permitted):
          
          if permitted not in VALID_SITE_CONTROL:
              raise TypeError(SITE_CONTROL_ERROR.format(permitted))
          if permitted == SITE_CONTROL_NONE:
              # Metapolicy 'none' means no access is permitted.
              self.domains = {}
              self.header_domains = {}
              self.identities = []
          self.site_control = permitted
docs: Sets metapolicy to ``permitted``. (only applicable to master
          policy files). Acceptable values correspond to those listed in
          Section 3(b)(i) of the crossdomain.xml specification, and are
          also available as a set of constants defined in this module.
  
          By default, Flash assumes a value of ``master-only`` for all
          policies except socket policies, (which assume a default of
          ``all``) so if this is desired (and, for security, it
          typically is), this method does not need to be called.
  
          Note that a metapolicy of ``none`` forbids **all** access,
          even if one or more domains, headers or identities have
          previously been specified as allowed. As such, setting the
          metapolicy to ``none`` will remove all access previously
          granted by ``allow_domain``, ``allow_headers`` or
          ``allow_identity``. Additionally, attempting to grant access
          via ``allow_domain``, ``allow_headers`` or ``allow_identity``
          will, when the metapolicy is ``none``, raise ``TypeError``.