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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def authorizer(self, schemes, resource, action, request_args):
 """Construct the Authorization header for a request. Args: schemes (list of str):
 Authentication schemes supported for the requested action. resource (str):
 Object upon which an action is being performed. action (str):
 Action being performed. request_args (list of str):
 Arguments passed to the action call. Returns: (str, str) A tuple of the auth scheme satisfied, and the credential for the Authorization header or empty strings if none could be satisfied. """

        if not schemes:
            return u'', u''
        for scheme in schemes:
            if scheme in self.schemes and self.has_auth_params(scheme):
                cred = Context.format_auth_params(self.schemes[scheme][u'params'])
                if hasattr(self, 'mfa_token'):
                    cred = '{}, mfa_token="{}"'.format(cred, self.mfa_token)
                return scheme, cred

        raise AuthenticationError(self, schemes)