docs: def AmiName(ami_release_name, ubuntu_release_name, virtualization_type,
              mapr_version, role):
    """ Returns AMI name using Cirrus ami naming convention. """
    if not role in valid_instance_roles:
      raise RuntimeError('Specified role (%s) not a valid role: %s' %
                           (role, valid_instance_roles))
    if virtualization_type not in valid_virtualization_types:
      raise RuntimeError('Specified virtualization type (%s) not valid: %s' %
                           (virtualization_type, valid_virtualization_types))
    ami_name = 'cirrus-%s-ubuntu-%s-%s-mapr%s-%s' % (ami_release_name,
                                                     ubuntu_release_name,
                                                     virtualization_type,
                                                     mapr_version, role)
    return ami_name