module Sequel::Dataset::UnnumberedArgumentMapper

def map_to_prepared_args(bind_vars)

have multiple entries in the output array.
Keys in the input hash that are used more than once in the query
Returns a single output array mapping the values of the input hash. 
def map_to_prepared_args(bind_vars)
  prepared_args.map{|v| bind_vars[v]}
end

def prepared_arg(k)

the output array.
Associates the argument with name k with the next position in 
def prepared_arg(k)
  prepared_args << k
  prepared_arg_placeholder
end

def prepared_arg?(k)

Always assume there is a prepared arg in the argument mapper. 
def prepared_arg?(k)
  true
end