def attributes_string_map
      @_attributes_string_map ||= {}.tap do |attr_hash|
        attributes_nil_hash.each_key { |k| attr_hash[k.to_sym] = k }
      end.freeze
    end
def attributes_string_map
      @_attributes_string_map ||= {}.tap do |attr_hash|
        attributes_nil_hash.each_key { |k| attr_hash[k.to_sym] = k }
      end.freeze
    end
During object wrapping, a props hash is built with string keys but Neo4j-core provides symbols.
 Rather than a `to_s` or `symbolize_keys` during every load, we build a map of symbol-to-string
 to speed up the process. This increases memory used by the gem but reduces object allocation and GC, so it is faster
 in practice.