code: def _field(self, field, value):
          
          # Fields and values must be strings for Elasticsearch
          field = str(field)
          value = str(value)
  
          # Check if quotes required and allowed, and quotes not present
          # If the user adds improper double-quotes, this will not fix them
          if (any([char in value for char in QUOTE_LIST]) and '"' not in value
                  and not any([char in value for char in UNQUOTE_LIST])):
              value = '"' + value + '"'
  
          # Cannot add field:value if one is blank
          if field and value:
              self.__query["q"] += field + ":" + value
              # Field matches are advanced queries
              self.__query["advanced"] = True
  
          return self
docs: Add a ``field:value`` term to the query.
          Matches will have the ``value`` in the ``field``.
  
          Note:
              This method triggers advanced mode.
  
          Arguments:
              field (str): The field to check for the value, in Elasticsearch dot syntax.
              value (str): The value to match.
  
          Returns:
              SearchHelper: Self