todo

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0003: Improve database
In the init database I would like to use class properties instead of get/read
line: 263,273,and 394
    def create(self)
should be replaced by:
    @property
    def create(self)

It implies that at every point that self.create() is called should be changed to self.create [Note the absence of parenthesis]

line: 298
    def get_posorients(self) 
should be replaced by
    @property
    def posorients(self)

Need to propagate the changes through all the code (see rendering / processing / moving )
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0004: Change every assert by a if () raise TypeError/IOError/KeyError/... 
- present in processing
- present in database

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0005: Write test function for raise Error
- for every raise error create a test function, checking that the error is correctly thrown (see moving/test_agent for inspiration)

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0006: Improve comparing/__init__.py
- Change comment in simple_image_diff
- call simple_image_diff in imagediff. you can then remove all the assert (that should be raise Error at that point) from imagediff
- Add comment to diff_optic_flow / add reference to article. 
- rename capitalised variable A,ATA, and b as longer variable name [future PEP8 will forbid this]

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0007: Improve cyber_bee so that every getter and setter are properties

0008: Improve bee_sampling so that every getter and setter are properties
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0009: can the last dimension (4) of the place-code be greater 1? (should be 1)
0010: what is the image in the database? must it be transformed to a a scene?