class ActiveSupport::Callbacks::Callback

def make_lambda(filter)

the same after this point.
All of these objects are converted into a lambda and handled

Objects:: An object with a before_foo method on it to call.
Procs:: A proc to call with the object.
Strings:: Some content to evaluate.
Symbols:: A method to call.

Filters support: 
def make_lambda(filter)
  case filter
  when Symbol
    lambda { |target, _, &blk| target.send filter, &blk }
  when String
    l = eval "lambda { |value| #{filter} }"
    lambda { |target, value| target.instance_exec(value, &l) }
  when Conditionals::Value then filter
  when ::Proc
    if filter.arity > 1
      return lambda { |target, _, &block|
        raise ArgumentError unless block
        target.instance_exec(target, block, &filter)
      }
    end
    if filter.arity <= 0
      lambda { |target, _| target.instance_exec(&filter) }
    else
      lambda { |target, _| target.instance_exec(target, &filter) }
    end
  else
    scopes = Array(chain_config[:scope])
    method_to_call = scopes.map{ |s| public_send(s) }.join("_")
    lambda { |target, _, &blk|
      filter.public_send method_to_call, target, &blk
    }
  end
end