18.8. "MimeWriter" — Generic MIME file writer
*********************************************

Deprecated since version 2.3: The "email" package should be used in
preference to the "MimeWriter" module.  This module is present only to
maintain backward compatibility.

This module defines the class "MimeWriter".  The "MimeWriter" class
implements a basic formatter for creating MIME multi-part files.  It
doesn’t seek around the output file nor does it use large amounts of
buffer space. You must write the parts out in the order that they
should occur in the final file. "MimeWriter" does buffer the headers
you add, allowing you to rearrange their order.

class MimeWriter.MimeWriter(fp)

   Return a new instance of the "MimeWriter" class.  The only argument
   passed, *fp*, is a file object to be used for writing. Note that a
   "StringIO" object could also be used.


18.8.1. MimeWriter Objects
==========================

"MimeWriter" instances have the following methods:

MimeWriter.addheader(key, value[, prefix])

   Add a header line to the MIME message. The *key* is the name of the
   header, where the *value* obviously provides the value of the
   header. The optional argument *prefix* determines where the header
   is inserted; "0" means append at the end, "1" is insert at the
   start. The default is to append.

MimeWriter.flushheaders()

   Causes all headers accumulated so far to be written out (and
   forgotten). This is useful if you don’t need a body part at all,
   e.g. for a subpart of type *message/rfc822* that’s (mis)used to
   store some header-like information.

MimeWriter.startbody(ctype[, plist[, prefix]])

   Returns a file-like object which can be used to write to the body
   of the message.  The content-type is set to the provided *ctype*,
   and the optional parameter *plist* provides additional parameters
   for the content-type declaration. *prefix* functions as in
   "addheader()" except that the default is to insert at the start.

MimeWriter.startmultipartbody(subtype[, boundary[, plist[, prefix]]])

   Returns a file-like object which can be used to write to the body
   of the message.  Additionally, this method initializes the multi-
   part code, where *subtype* provides the multipart subtype,
   *boundary* may provide a user-defined boundary specification, and
   *plist* provides optional parameters for the subtype. *prefix*
   functions as in "startbody()".  Subparts should be created using
   "nextpart()".

MimeWriter.nextpart()

   Returns a new instance of "MimeWriter" which represents an
   individual part in a multipart message.  This may be used to write
   the  part as well as used for creating recursively complex
   multipart messages. The message must first be initialized with
   "startmultipartbody()" before using "nextpart()".

MimeWriter.lastpart()

   This is used to designate the last part of a multipart message, and
   should *always* be used when writing multipart messages.
