Methods to get accessors related to is_many accessor

This extracts the name resolution for property names related to is_many accessors.  With these, you can ask the class object what the iterator accessor is for a given is_many property name.
This might be more clear as "...accepts key/value pairs as arguments, which are used to filter..." or "and it is used to filter" if it's important that we're discussing the accessor and not the arguments.