Return the parameter list of the Content-Type: header.
This is a list of strings. For parameters of the form
"key=value", key is converted to lower case but
value is not. For example, if the message contains the header
"Content-type: text/html; spam=1; Spam=2; Spam" then
getplist() will return the Python list ['spam=1',
'spam=2', 'Spam'].
Return the value of the first parameter (as returned by
getplist() of the form "name=value" for the
given name. If value is surrounded by quotes of the form
`<...>' or `"..."', these are removed.
Return the encoding specified in the
Content-Transfer-Encoding: message header. If no such
header exists, return '7bit'. The encoding is converted to
lower case.
Return the message type (of the form "type/subtype")
as specified in the Content-Type: header. If no such
header exists, return 'text/plain'. The type is converted to
lower case.