'Deletes an existing ``RankExpression`` from the search domain.
:type domain_name: string
:param domain_name: A string that represents the name of a
domain. Domain names must be unique across the domains
owned by an account within an AWS region. Domain names
must start with a letter or number and can contain the
following characters: a-z (lowercase), 0-9, and -
(hyphen). Uppercase letters and underscores are not
allowed.
:type rank_name: string
:param rank_name: Name of the ``RankExpression`` to delete.
:raises: BaseException, InternalException, ResourceNotFoundException'

def delete_rank_expression(self, domain_name, rank_name):

    doc_path = ('delete_rank_expression_response', 'delete_rank_expression_result', 'rank_expression')
    params = {'DomainName': domain_name, 'RankName': rank_name}
    return self.get_response(doc_path, 'DeleteRankExpression', params, verb='POST')
