Traceback (most recent call last): File "alphabeta.py", line 230, in File "alphabeta.py", line 25, in __init__ File "alphabeta.py", line 215, in initialize_tracker File "alphabeta.py", line 185, in update_trajectory File "matplotlib\backends\backend_tkagg.pyc", line 215, in draw File "matplotlib\backends\backend_agg.pyc", line 314, in draw File "matplotlib\artist.pyc", line 46, in draw_wrapper File "matplotlib\figure.pyc", line 773, in draw File "matplotlib\artist.pyc", line 46, in draw_wrapper File "matplotlib\axes.pyc", line 1735, in draw File "matplotlib\text.pyc", line 515, in draw File "matplotlib\text.pyc", line 279, in _get_layout File "matplotlib\backends\backend_agg.pyc", line 156, in get_text_width_height_descent File "matplotlib\mathtext.pyc", line 2810, in parse File "matplotlib\mathtext.pyc", line 2259, in parse File "matplotlib\pyparsing.pyc", line 1048, in parseString File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2559, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2307, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2672, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2307, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2756, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2706, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2373, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2559, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2416, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2559, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2559, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2416, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2293, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2756, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2559, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2373, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 924, in _parseNoCache File "matplotlib\pyparsing.pyc", line 2416, in parseImpl File "matplotlib\pyparsing.pyc", line 981, in _parseCache File "matplotlib\pyparsing.pyc", line 950, in _parseNoCache File "matplotlib\mathtext.pyc", line 2374, in symbol File "matplotlib\mathtext.pyc", line 1264, in __init__ File "matplotlib\mathtext.pyc", line 1271, in _update_metrics File "matplotlib\mathtext.pyc", line 446, in get_metrics File "matplotlib\mathtext.pyc", line 579, in _get_info File "matplotlib\mathtext.pyc", line 676, in _get_glyph File "matplotlib\mathtext.pyc", line 560, in _get_font TypeError: cannot return std::string from Unicode object