'Send an email.
`to_address` is a string or list of string email addresses.
`from_address` is a email address.
`subject` is the email\'s subject.
`text` is the text of the email.
`reply_to` is the reply-to address, which will be sent as the "Reply-To"
email header.
`parent_email_id` is the Message-Id of the email this is a reply to (if
any). This is sent as the "In-Reply-To" email header.
`other_email_ids` is a list of Message-Ids of emails in the conversation
and including `parent_email_id`. This will be converted to a space
delimited string and sent as the "References" email header.
The return value is the Message-Id of the sent email.'

def send_email(self, to_address, from_address, subject, text, reply_to, parent_email_id=None, other_email_ids=None):

    raise NotImplementedError
