def inherited_fields
      return [] unless has_parent?

      names = parent.fields.keys - fields.keys
      names.concat(parent.aliases.reject { |k,v| !parent.has_field?(v) }.keys)
      names.sort!

      names
    end
def inherited_fields
      return [] unless has_parent?

      names = parent.fields.keys - fields.keys
      names.concat(parent.aliases.reject { |k,v| !parent.has_field?(v) }.keys)
      names.sort!

      names
    end
Returns a sorted list of all field names referenced by this Entry's cross-reference.