module Hashie::Extensions::Coercion::ClassMethods

def build_hash_coercion(type, key_type, value_type)
  key_coerce = fetch_coercion(key_type)
  value_coerce = fetch_coercion(value_type)
  lambda do |value|
    type[value.map { |k, v| [key_coerce.call(k), value_coerce.call(v)] }]
  end
end