Content-Type: multipart/mixed; boundary="1"

--1
Content-Type: multipart/mixed; boundary="2"

--2
Content-Type: message/rfc822

Content-Type: text/plain

1
--2
Content-Type: message/rfc822

Content-Type: text/plain

22
--1
Content-Type: message/rfc822

Content-Type: text/plain

333

---- EXPECTED STRUCTURE ----
{
  "headers_rfc": {
    "content_type": {
      "ContentType": {
        "c_type": "multipart",
        "c_subtype": "mixed",
        "attributes": {
          "boundary": "1"
        }
      }
    }
  },
  "headers_offsets": [
    {
      "name": {
        "Rfc": "content_type"
      },
      "start": 13,
      "end": 44
    }
  ],
  "attachments": [
    1,
    2
  ],
  "parts": [
    {
      "Multipart": {
        "content_type": {
          "ContentType": {
            "c_type": "multipart",
            "c_subtype": "mixed",
            "attributes": {
              "boundary": "2"
            }
          }
        }
      }
    },
    {
      "Message": {
        "headers": {
          "content_type": {
            "ContentType": {
              "c_type": "message",
              "c_subtype": "rfc822"
            }
          }
        },
        "body": {
          "headers_rfc": {
            "content_type": {
              "ContentType": {
                "c_type": "text",
                "c_subtype": "plain"
              }
            }
          },
          "headers_offsets": [
            {
              "name": {
                "Rfc": "content_type"
              },
              "start": 141,
              "end": 153
            }
          ],
          "html_body": [
            0
          ],
          "text_body": [
            0
          ],
          "parts": [
            {
              "Text": {
                "body": "1"
              }
            }
          ],
          "structure": {
            "Part": 0
          },
          "offset_header": 128,
          "offset_body": 154,
          "offset_end": 160
        }
      }
    },
    {
      "Message": {
        "headers": {
          "content_type": {
            "ContentType": {
              "c_type": "message",
              "c_subtype": "rfc822"
            }
          }
        },
        "body": {
          "headers_rfc": {
            "content_type": {
              "ContentType": {
                "c_type": "text",
                "c_subtype": "plain"
              }
            }
          },
          "headers_offsets": [
            {
              "name": {
                "Rfc": "content_type"
              },
              "start": 203,
              "end": 215
            }
          ],
          "attachments": [
            0
          ],
          "parts": [
            {
              "Text": {
                "body": "22\n--1\nContent-Type: message/rfc822\n\nContent-Type: text/plain\n\n333\n"
              }
            }
          ],
          "structure": {
            "Part": 0
          },
          "offset_header": 190,
          "offset_body": 216,
          "offset_end": 283
        }
      }
    }
  ],
  "structure": {
    "MultiPart": [
      0,
      []
    ]
  },
  "offset_header": 0,
  "offset_body": 45,
  "offset_end": 283
}