code: func (s *SearchDsl) Filter(fl *FilterOp) *SearchDsl {
  	s.FilterVal = fl
  	return s
  }
docs: // Filter adds a Filter Clause with optional Boolean Clause.  This accepts n number of
  // filter clauses.  If more than one, and missing Boolean Clause it assumes "and"
  //
  //     qry := Search("github").Filter(
  //         Filter().Exists("repository.name"),
  //     )
  //
  //     qry := Search("github").Filter(
  //         "or",
  //         Filter().Exists("repository.name"),
  //         Filter().Terms("actor_attributes.location", "portland"),
  //     )
  //
  //     qry := Search("github").Filter(
  //         Filter().Exists("repository.name"),
  //         Filter().Terms("repository.has_wiki", true)
  //     )