def relation_names(inclusions)
      inclusions.is_a?(Hash) ? inclusions.keys : Array.wrap(inclusions)
    end
def relation_names(inclusions)
      inclusions.is_a?(Hash) ? inclusions.keys : Array.wrap(inclusions)
    end
Since the inclusions can be a hash, symbol, or array of symbols, this is
 provided as a convenience to parse out the names.

 @example Get the association names.
   document.relation_names(:include => [ :addresses ])

 @param [ Hash, Symbol, Array<Symbol> ] inclusions The inclusions.

 @return [ Array<Symbol> ] The names of the included associations.

 @since 2.0.0.rc.6