def member_exists(self, member_id):
request_url = build_url_endpoint(<EOL>'<STR_LIT:/>'.join([self.ENDPOINT, str(member_id)])<EOL>)<EOL>request_params = {}<EOL>result = self.do_http_request(<EOL>'<STR_LIT>',<EOL>request_url,<EOL>data=request_params,<EOL>only_headers=True,<EOL>custom_header=str(self.etiquette)<EOL>)<EOL>if result.status_code == <NUM_LIT>:<EOL><INDENT>return False<EOL><DEDENT>return True<EOL>
This method retrieve a boolean according to the existence of a crossref
member. It returns False if the API results a 404 status code.

args: Crossref allowed document Type (String)

return: Boolean

Example 1:
    >>> from crossref.restful import Members
    >>> members = Members()
    >>> members.member_exists(101)
    True

Example 2:
    >>> from crossref.restful import Members
    >>> members = Members()
    >>> members.member_exists(88888)
    False