Content-Type: multipart/mixed; boundary=":foo"

--:foo
--:foo
Content-Type: text/plain
--:foo
Content-Type: text/plain
--:foo
Content-Type: text/html
--:foo--

---- EXPECTED STRUCTURE ----
{
  "headers_rfc": {
    "content_type": {
      "ContentType": {
        "c_type": "multipart",
        "c_subtype": "mixed",
        "attributes": {
          "boundary": ":foo"
        }
      }
    }
  },
  "headers_other": {},
  "headers_offsets": [
    {
      "name": {
        "Rfc": "content_type"
      },
      "start": 13,
      "end": 47
    }
  ],
  "html_body": [
    0,
    1
  ],
  "text_body": [
    0,
    1
  ],
  "attachments": [],
  "parts": [
    {
      "Text": {
        "headers": {},
        "body": "Content-Type: text/plain"
      }
    },
    {
      "Text": {
        "headers": {
          "content_type": {
            "ContentType": {
              "c_type": "text",
              "c_subtype": "plain",
              "attributes": null
            }
          }
        },
        "body": "Content-Type: text/html"
      }
    }
  ],
  "structure": {
    "List": [
      {
        "Part": 0
      },
      {
        "Part": 1
      }
    ]
  },
  "offset_header": 0,
  "offset_body": 48,
  "offset_end": 159
}