def agency(self, doi, only_message=True):
request_url = build_url_endpoint(<EOL>'<STR_LIT:/>'.join([self.ENDPOINT, doi, '<STR_LIT>'])<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 the DOI Agency metadata related to a given DOI
number.

args: Crossref DOI id (String)

return: JSON

Example:
    >>> from crossref.restful import Works
    >>> works = Works()
    >>> works.agency('10.1590/S0004-28032013005000001')
    {'DOI': '10.1590/s0004-28032013005000001', 'agency': {'label': 'CrossRef', 'id': 'crossref'}}