def dependency(key, dependency)
      raise_error(type: "dependency", key: "key", needed: dependency) unless validator.datas.has_key?(dependency)
    end
def dependency(key, dependency)
      raise_error(type: "dependency", key: "key", needed: dependency) unless validator.datas.has_key?(dependency)
    end
Checks if a dependency is respected. A dependency is a key openly needed by another key.
 @param [Object] key the key needing another key to properly work.
 @param [Object] dependency the key needed by another key for it to properly work.
 @raise [ArgumentError] if the required dependency is not present.