'Configures an `IndexField` for the search domain. Used to
create new fields and modify existing ones. You must specify
the name of the domain you are configuring and an index field
configuration. The index field configuration specifies a
unique name, the index field type, and the options you want to
configure for the field. The options you can specify depend on
the `IndexFieldType`. If the field exists, the new
configuration replaces the old one. For more information, see
`Configuring Index Fields`_ in the Amazon CloudSearch
Developer Guide .
:type domain_name: string
:param domain_name: A string that represents the name of a domain.
Domain names are unique across the domains owned by an account
within an AWS region. Domain names start with a letter or number
and can contain the following characters: a-z (lowercase), 0-9, and
- (hyphen).
:type index_field: dict
:param index_field: The index field and field options you want to
configure.'

def define_index_field(self, domain_name, index_field):

    params = {'DomainName': domain_name}
    self.build_complex_param(params, 'IndexField', index_field)
    return self._make_request(action='DefineIndexField', verb='POST', path='/', params=params)
