def journal(self, issn, only_message=True):
request_url = build_url_endpoint(<EOL>'<STR_LIT:/>'.join([self.ENDPOINT, str(issn)])<EOL>)<EOL>request_params = {}<EOL>result = self.do_http_request(<EOL>'<STR_LIT>',<EOL>request_url,<EOL>data=request_params,<EOL>custom_header=str(self.etiquette)<EOL>)<EOL>if result.status_code == <NUM_LIT>:<EOL><INDENT>return<EOL><DEDENT>result = result.json()<EOL>return result['<STR_LIT:message>'] if only_message is True else result<EOL>
This method retrieve a json with the given ISSN metadata

args: Journal ISSN (String)

return: Journal JSON data

Example:
    >>> from crossref.restful import Journals
    >>> journals = Journals()
    >>> journals.journal('2277-338X')
    {'last-status-check-time': None, 'counts': None, 'coverage': None,
    'publisher': 'ScopeMed International Medical Journal Managment and Indexing System',
    'flags': None, 'breakdowns': None, 'ISSN': ['2320-4664', '2277-338X'],
    'title': 'International Journal of Medical Science and Public Health'}