rule_info {
  rule_name: "my_rule"
  doc_string: "This is my rule. It does stuff."
  attribute {
    name: "name"
    doc_string: "A unique name for this target."
    type: NAME
    mandatory: true
  }
  attribute {
    name: "first"
    doc_string: "first my_rule doc string"
    type: LABEL
    mandatory: true
  }
  attribute {
    name: "second"
    type: STRING_DICT
    mandatory: true
  }
}
module_docstring: "A direct dependency file of the input file."