def add_to(self, email):
if email.substitutions:<EOL><INDENT>if isinstance(email.substitutions, list):<EOL><INDENT>for substitution in email.substitutions:<EOL><INDENT>self.add_substitution(substitution)<EOL><DEDENT><DEDENT>else:<EOL><INDENT>self.add_substitution(email.substitutions)<EOL><DEDENT><DEDENT>if email.subject:<EOL><INDENT>if isinstance(email.subject, str):<EOL><INDENT>self.subject = email.subject<EOL><DEDENT>else:<EOL><INDENT>self.subject = email.subject.get()<EOL><DEDENT><DEDENT>self._tos.append(email.get())<EOL>
Add a single recipient to this Personalization.

        :type email: Email