The global dictionary SD is available to store private data between repeated calls to the same function. The global dictionary GD is public data, that is available to all Python functions within a session; use with care.
Each function gets its own execution environment in the Python interpreter, so that global data and function arguments from myfunc are not available to myfunc2. The exception is the data in the GD dictionary, as mentioned above.
Read the upstream documentation. For corrections, first check the current version.