old_contents: class HttpMethod(object):
      HEAD = 'HEAD'
      GET = 'GET'
      POST = 'POST'
      PUT = 'PUT'
      DELETE = 'DELETE'
  
  
  class ResponseCodes(object):
      OK = 200
      CREATED = 201
      ACCEPTED = 202
      BAD_REQUEST = 400
      NOT_FOUND = 404
  
  
  class HostParsing(object):
      HTTP = 'http'
      HTTPS = 'https'
      USE_SSL = 'use_ssl'
      URL_PREFIX = 'url_prefix'
      SCHEME = 'scheme'
      HTTP_AUTH = 'http_auth'
      PORT = 'port'
      HOST = 'host'
  
  
  class EsMethods(object):
      MULTIPLE_SEARCH = '_msearch'
      BULK = '_bulk'
      COUNT = '_count'
      EXPLAIN = '_explain'
      MULTIPLE_GET = '_mget'
      UPDATE = '_update'
      SOURCE = '_source'
      SEARCH = '_search'
      SCROLL = 'scroll'
  
  
  class EsConst(object):
      TOTAL = 'total'
      FAILED = 'failed'
      SHARDS = '_shards'
      ALL_VALUES = '_all'
      FIELDS = 'fields'
      SCROLL_ID = 'scroll_id'
      HITS = 'hits'
      FOUND = 'found'
  
  
  class EsBulk(object):
      OP_TYPE = '_op_type'
      INDEX = 'index'
      CREATE = 'create'
      DELETE = 'delete'
      UPDATE = 'update'
  
  
  class EsDocProperties(object):
      INDEX = '_index'
      TYPE = '_type'
      PARENT = '_parent'
      PERCOLATE = '_percolate'
      ROUTING = '_routing'
      TIMESTAMP = '_timestamp'
      TTL = '_ttl'
      VERSION = '_version'
      VERSION_TYPE = '_version_type'
      ID = '_id'
      RETRY_ON_CONFLICT = '_retry_on_conflict'
      SOURCE = '_source'
      SCROLL_ID = '_scroll_id'
  
  
  class EsAggregation(object):
      AGGREGATIONS = 'aggregations'
      BUCKETS = 'buckets'
      DOC_COUNT = 'doc_count'
      KEY = 'key'
  
  
  # parts of URL to be omitted
  NULL_VALUES = (None, '', b'', [], ())
  
new_contents: class HttpMethod(object):
      HEAD = 'HEAD'
      GET = 'GET'
      POST = 'POST'
      PUT = 'PUT'
      DELETE = 'DELETE'
  
  
  class ResponseCodes(object):
      OK = 200
      CREATED = 201
      ACCEPTED = 202
      BAD_REQUEST = 400
      NOT_FOUND = 404
  
  
  class HostParsing(object):
      HTTP = 'http'
      HTTPS = 'https'
      USE_SSL = 'use_ssl'
      URL_PREFIX = 'url_prefix'
      SCHEME = 'scheme'
      HTTP_AUTH = 'http_auth'
      PORT = 'port'
      HOST = 'host'
  
  
  class EsMethods(object):
      MULTIPLE_SEARCH = '_msearch'
      BULK = '_bulk'
      COUNT = '_count'
      EXPLAIN = '_explain'
      MULTIPLE_GET = '_mget'
      UPDATE = '_update'
      SOURCE = '_source'
      SEARCH = '_search'
      SCROLL = 'scroll'
  
  
  class EsConst(object):
      TOTAL = 'total'
      FAILED = 'failed'
      SHARDS = '_shards'
      ALL_VALUES = '_all'
      FIELD = 'field'
      FIELDS = 'fields'
      SCROLL_ID = 'scroll_id'
      HITS = 'hits'
      FOUND = 'found'
  
  
  class EsBulk(object):
      OP_TYPE = '_op_type'
      INDEX = 'index'
      CREATE = 'create'
      DELETE = 'delete'
      UPDATE = 'update'
  
  
  class EsDocProperties(object):
      INDEX = '_index'
      TYPE = '_type'
      PARENT = '_parent'
      PERCOLATE = '_percolate'
      ROUTING = '_routing'
      TIMESTAMP = '_timestamp'
      TTL = '_ttl'
      VERSION = '_version'
      VERSION_TYPE = '_version_type'
      ID = '_id'
      RETRY_ON_CONFLICT = '_retry_on_conflict'
      SOURCE = '_source'
      SCROLL_ID = '_scroll_id'
  
  
  class EsAggregation(object):
      AGGREGATIONS = 'aggregations'
      BUCKETS = 'buckets'
      DOC_COUNT = 'doc_count'
      KEY = 'key'
      AGGS = 'aggs'
  
  
  class EsQuery(object):
      SIZE = 'size'
      QUERY = 'query'
      BOOL = 'bool'
      MUST = 'must'
      MUST_NOT = 'must_not'
      SHOULD = 'should'
      MATCH_ALL = 'match_all'
      MATCH = 'match'
      TERMS = 'terms'
      FILTER = 'filter'
      CONSTANT_SCORE = 'constant_score'
  
  
  # parts of URL to be omitted
  NULL_VALUES = (None, '', b'', [], ())
  
subject: add basic query consts (#34)