docs: def init_headers(self, x_auth_token, tenant_id, content_type=HEADER_REPRESENTATION_XML,
                       transaction_id=generate_transaction_id()):
          """
          Init header to values (or default values)
          :param x_auth_token: Token from Keystone for tenant_id (OpenStack)
          :param tenant_id: TenantId (OpenStack)
          :param content_type: Content-Type header value. By default application/xml
          :param transaction_id: txId header value. By default, generated value by generate_transaction_id()
          :return: None
          """
  
          logger.debug("Init headers")
          if content_type is None:
              if HEADER_CONTENT_TYPE in self.headers:
                  del(self.headers[HEADER_CONTENT_TYPE])
          else:
              self.headers.update({HEADER_CONTENT_TYPE: content_type})
  
          if transaction_id is None:
              if HEADER_TRANSACTION_ID in self.headers:
                  del(self.headers[HEADER_TRANSACTION_ID])
          else:
              self.headers.update({HEADER_TRANSACTION_ID: transaction_id})
  
          self.headers.update({X_AUTH_TOKEN: x_auth_token})
  
          self.headers.update({TENANT_ID: tenant_id})
  
          logger.debug("Headers: " + str(self.headers))