code: def _check_pool_attr(self, attr, req_attr=None):
          
  
          if req_attr is None:
              req_attr = []
  
          # check attribute names
          self._check_attr(attr, req_attr, _pool_attrs)
  
          # validate IPv4 prefix length
          if attr.get('ipv4_default_prefix_length') is not None:
              try:
                  attr['ipv4_default_prefix_length'] = \
                      int(attr['ipv4_default_prefix_length'])
  
                  if (attr['ipv4_default_prefix_length'] > 32 or
                      attr['ipv4_default_prefix_length'] < 1):
                      raise ValueError()
              except ValueError:
                  raise NipapValueError('Default IPv4 prefix length must be an integer between 1 and 32.')
  
          # validate IPv6 prefix length
          if attr.get('ipv6_default_prefix_length'):
              try:
                  attr['ipv6_default_prefix_length'] = \
                      int(attr['ipv6_default_prefix_length'])
  
                  if (attr['ipv6_default_prefix_length'] > 128 or
                      attr['ipv6_default_prefix_length'] < 1):
                      raise ValueError()
              except ValueError:
                  raise NipapValueError('Default IPv6 prefix length must be an integer between 1 and 128.')
docs: Check pool attributes.