API global error code

<table> <thead> <tr> <th>Error Code</th> <th>Misexplain</th> </tr> </thead> <tbody> <tr> <td>2000</td> <td>sign certification failed</td> </tr> <tr> <td>2001</td> <td>request timeout</td> </tr> <tr> <td>2002</td> <td>institution does not open an open interface</td> </tr> <tr> <td>2003</td> <td>class section ID is empty</td> </tr> <tr> <td>2004</td> <td>class section does not exist or has been deleted</td> </tr> <tr> <td>2005</td> <td>class section has started</td> </tr> <tr> <td>2006</td> <td>class section is over</td> </tr> <tr> <td>2010</td> <td>institution does not exist</td> </tr> <tr> <td>2012</td> <td>jump link generation failed, please check the parameters</td> </tr> <tr> <td>2013</td> <td>the number of students exceeds the limit of 30</td> </tr> <tr> <td>2014</td> <td>can not add a teacher to the student list</td> </tr> <tr> <td>2015</td> <td>users are not students of this class section</td> </tr> <tr> <td>2016</td> <td>users are not teachers of this class section</td> </tr> <tr> <td>2101</td> <td>folder or file id is empty</td> </tr> <tr> <td>2102</td> <td>folder or file name is empty</td> </tr> <tr> <td>2103</td> <td>upload file binary file stream cannot be empty</td> </tr> <tr> <td>2104</td> <td>folder name is empty</td> </tr> <tr> <td>2105</td> <td>binary file parsing error</td> </tr> <tr> <td>2106</td> <td>class setion icloud information does not exist</td> </tr> <tr> <td>321</td> <td>parameter format error</td> </tr> <tr> <td>500</td> <td>unknown exception on the server</td> </tr> </tbody> </table>