text: # Python imports
  from typing import List, Generic
  
  # Project imports
  from src.utils import AddToken, SrchToken
  
  
  class SigmaServer(Generic[AddToken, SrchToken]):
      """Server interface of a wildcard supporting SSE scheme to be used for a Libertas server."""
  
      def __init__(
              self,
      ) -> None:
          """Initializes a server.
  
          :returns: None
          :rtype: None
          """
          pass
  
      def build_index(
              self,
      ) -> None:
          """Sets up the server, initializing its index.
  
          :returns: None
          :rtype: None
          """
          pass
  
      def search(
              self,
              srch_token: SrchToken,
      ) -> List[int]:
          """Searches the index for a query represented by a search token and returns matching document identifiers.
  
          :param srch_token: The search token
          :type srch_token: SrchToken
          :returns: A list of results
          :rtype: List[int]
          """
  
      def add(
              self,
              add_token: AddToken,
      ) -> None:
          """Adds a document-keyword pair, represented by an add token, to the index.
  
          :param add_token: An add token representing a document-keyword pair
          :type add_token: AddToken
          :returns: None
          :rtype: None
          """
          pass
  