<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_oauth_signature(self, request):
 """Get an OAuth signature to be used in signing a request To satisfy `section 3.4.1.2`_ item 2, if the request argument's headers dict attribute contains a Host item, its value will replace any netloc part of the request argument's uri attribute value. .. _`section 3.4.1.2`: https://tools.ietf.org/html/rfc5849#section-3.4.1.2 """

        if self.signature_method == SIGNATURE_PLAINTEXT:
            # fast-path
            return signature.sign_plaintext(self.client_secret,
                                            self.resource_owner_secret)

        uri, headers, body = self._render(request)

        collected_params = signature.collect_parameters(
            uri_query=urlparse.urlparse(uri).query,
            body=body,
            headers=headers)
        log.debug("Collected params: {0}".format(collected_params))

        normalized_params = signature.normalize_parameters(collected_params)
        normalized_uri = signature.base_string_uri(uri, headers.get('Host', None))
        log.debug("Normalized params: {0}".format(normalized_params))
        log.debug("Normalized URI: {0}".format(normalized_uri))

        base_string = signature.signature_base_string(request.http_method,
                                                      normalized_uri, normalized_params)

        log.debug("Signing: signature base string: {0}".format(base_string))

        if self.signature_method not in self.SIGNATURE_METHODS:
            raise ValueError('Invalid signature method.')

        sig = self.SIGNATURE_METHODS[self.signature_method](base_string, self)

        log.debug("Signature: {0}".format(sig))
        return sig