class Ransack::Nodes::Grouping

def attribute_method?(name)
  name = strip_predicate_and_index(name)
  case name
  when /^(g|c|m|groupings|conditions|combinator)=?$/
    true
  else
    name.split(/_and_|_or_/).select {|n| !@context.attribute_method?(n)}.empty?
  end
end