'Tells the search domain to start scanning its documents using
the latest text processing options and ``IndexFields``.  This
operation must be invoked to make visible in searches any
options whose <a>OptionStatus</a> has ``OptionState`` of
``RequiresIndexDocuments``.
: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.
:raises: BaseException, InternalException, ResourceNotFoundException'

def index_documents(self, domain_name):

    doc_path = ('index_documents_response', 'index_documents_result', 'field_names')
    params = {'DomainName': domain_name}
    return self.get_response(doc_path, 'IndexDocuments', params, verb='POST', list_marker='FieldNames')
