Connector: Fix Register membership test operator

I just removed the `__contains__` method because it is breaking membership tests that were working before since `has_key` was used instead. I believe it's not necessary as, if implemented correctly, the behavior would be the same as of  `dict.__contains__`. 
89:1: E302 expected 2 blank lines, found 1
89: D203 Expected 1 blank line *before* class docstring, found 0
89: D204 Expected 1 blank line *after* class docstring, found 0
89: D400 First line should end with '.', not 'g'
89: D205 Blank line missing between one-line summary and description
94: D205 Blank line missing between one-line summary and description
102:5: E301 expected 1 blank line, found 0
102: D205 Blank line missing between one-line summary and description
110:1: E302 expected 2 blank lines, found 1
110: D203 Expected 1 blank line *before* class docstring, found 0
110: D204 Expected 1 blank line *after* class docstring, found 0
110: D400 First line should end with '.', not 'o'
110: D205 Blank line missing between one-line summary and description
115: D205 Blank line missing between one-line summary and description
123:5: E301 expected 1 blank line, found 0
123: D205 Blank line missing between one-line summary and description
131:1: E302 expected 2 blank lines, found 1
131: D203 Expected 1 blank line *before* class docstring, found 0
131: D400 First line should end with '.', not 'o'
131: D200 One-line docstring should not occupy 3 lines
165:16: E711 comparison to None should be 'if cond is None:'
166:49: E261 at least two spaces before inline comment
167:18: E711 comparison to None should be 'if cond is None:'
189:95: E502 the backslash is redundant between brackets
190:87: E502 the backslash is redundant between brackets
193: D400 First line should end with '.', not 'n'
193: D205 Blank line missing between one-line summary and description
215:12: E713 test for membership should be 'not in'
218: D401 First line should be imperative: 'Return', not 'Returns'
286:64: E502 the backslash is redundant between brackets
287:25: E128 continuation line under-indented for visual indent
294: D401 First line should be imperative: 'Thi', not 'This'
294: D400 First line should end with '.', not ')'
294: D205 Blank line missing between one-line summary and description
326: D401 First line should be imperative: 'Return', not 'Returns'
326: D400 First line should end with '.', not 'e'
326: D200 One-line docstring should not occupy 3 lines
332: D401 First line should be imperative: 'Return', not 'Returns'
332: D400 First line should end with '.', not 'e'
332: D200 One-line docstring should not occupy 3 lines
338: D401 First line should be imperative: 'Return', not 'Returns'
338: D400 First line should end with '.', not 'd'
338: D200 One-line docstring should not occupy 3 lines
348:63: E502 the backslash is redundant between brackets
349:25: E128 continuation line under-indented for visual indent
351:61: E502 the backslash is redundant between brackets
352:25: E128 continuation line under-indented for visual indent
360: D401 First line should be imperative: 'Return', not 'Returns'
360: D400 First line should end with '.', not 'd'
360: D200 One-line docstring should not occupy 3 lines
369: D401 First line should be imperative: 'Upload', not 'Uploads'
369: D400 First line should end with '.', not 'r'
383:28: W602 deprecated form of raising exception
387:78: E502 the backslash is redundant between brackets
396:41: E127 continuation line over-indented for visual indent
402: D401 First line should be imperative: 'Parse', not 'Parses'
416: D401 First line should be imperative: 'Validate', not 'Validates'
416: D400 First line should end with '.', not 'l'
441: D203 Expected 1 blank line *before* class docstring, found 0
441: D204 Expected 1 blank line *after* class docstring, found 0
441: D400 First line should end with '.', not 'd'
441: D200 One-line docstring should not occupy 3 lines
445: D102 Docstring missing
454: D102 Docstring missing
463: D102 Docstring missing
476: D102 Docstring missing
479: D102 Docstring missing
482: D401 First line should be imperative: 'Return', not 'Returns'
482: D400 First line should end with '.', not 't'
482: D200 One-line docstring should not occupy 3 lines
488: D401 First line should be imperative: 'Return', not 'Returns'
488: D205 Blank line missing between one-line summary and description
494:13: E125 continuation line with same indent as next logical line
495:41: E225 missing whitespace around operator
495:60: E225 missing whitespace around operator
499: D203 Expected 1 blank line *before* class docstring, found 0
499: D204 Expected 1 blank line *after* class docstring, found 0
499: D200 One-line docstring should not occupy 3 lines
519: D101 Docstring missing
520: D401 First line should be imperative: 'Thi', not 'This'
520: D400 First line should end with '.', not 't'
520: D205 Blank line missing between one-line summary and description
530: D200 One-line docstring should not occupy 3 lines
545:1: E302 expected 2 blank lines, found 1
545: D203 Expected 1 blank line *before* class docstring, found 0
545: D400 First line should end with '.', not 'r'
545: D300 Expected """-quotes, got '-quotes
548: D400 First line should end with '.', not ':'
548: D205 Blank line missing between one-line summary and description
568: D102 Docstring missing
586:27: E701 multiple statements on one line (colon)
588:27: E701 multiple statements on one line (colon)
604: D102 Docstring missing
616: D102 Docstring missing
642: D401 First line should be imperative: 'Decompose', not 'Decomposes'
642: D400 First line should end with '.', not 'e'
642: D200 One-line docstring should not occupy 3 lines
648:19: E701 multiple statements on one line (colon)
650:19: E701 multiple statements on one line (colon)
652:22: E701 multiple statements on one line (colon)