ranker: rank method function fix

Fixes issue that e.g. ``bibrank -w wrd`` will fail with ``Cannot run method 'wrd', no function to call``.
84:1: F401 'download_weight_total' imported but unused
84:1: F401 'citation' imported but unused
84:1: F401 'file_similarity_by_times_downloaded' imported but unused
84:1: F401 'single_tag_rank_method' imported but unused
84:1: F401 'index_term_count' imported but unused
84:1: F401 'download_weight_filtering_user' imported but unused
85:6: E126 continuation line over-indented for hanging indent
91:1: F401 'word_similarity' imported but unused
92:1: F401 'citerank' imported but unused
93:1: F401 'word_similarity_solr' imported but unused
95:1: F401 'word_similarity_xapian' imported but unused
97:1: F401 'selfcites' imported but unused
103:17: E261 at least two spaces before inline comment
104:25: E261 at least two spaces before inline comment
106:1: E302 expected 2 blank lines, found 1
106: D400 First line should end with '.', not 's'
113:27: E225 missing whitespace around operator
116:56: E261 at least two spaces before inline comment
123:1: E302 expected 2 blank lines, found 1
123: D401 First line should be imperative: 'Return', not 'Returns'
123: D400 First line should end with '.', not 'e'
123: D300 Expected """-quotes, got '-quotes
126:19: E225 missing whitespace around operator
129:19: E225 missing whitespace around operator
134:1: E302 expected 2 blank lines, found 1
134: D400 First line should end with '.', not 'k'
134: D205 Blank line missing between one-line summary and description
147:13: E128 continuation line under-indented for visual indent
153:17: E128 continuation line under-indented for visual indent
154:17: E128 continuation line under-indented for visual indent
165:17: E128 continuation line under-indented for visual indent
169:1: E302 expected 2 blank lines, found 1
173:13: E128 continuation line under-indented for visual indent
174:13: E128 continuation line under-indented for visual indent
182:13: E128 continuation line under-indented for visual indent
215:13: E128 continuation line under-indented for visual indent
216:13: E128 continuation line under-indented for visual indent
233:13: E128 continuation line under-indented for visual indent
234:17: E127 continuation line over-indented for visual indent
235:13: E128 continuation line under-indented for visual indent
242:17: E231 missing whitespace after ','
242:41: E231 missing whitespace after ','
243:32: W602 deprecated form of raising exception
255:50: E261 at least two spaces before inline comment
277:32: W602 deprecated form of raising exception
280:59: E261 at least two spaces before inline comment
280:59: E262 inline comment should start with '# '