Different mode of file loading.

Modes can be set by providing mode=.. keyword or explicitly by specifying read_only and overwrite options.

'w' mode is the same as

>>> sd = DH5('somedata.h5', read_only=False)

'a' mode is the same as

>>> sd = DH5('somedata.h5', read_only=False, overwrite=False)

'r' mode is the same as

>>> sd = DH5('somedata.h5', read_only=True)

DH5.open_overwrite method is the same as

>>> sd = DH5('somedata.h5', read_only=False, overwrite=True)
or
>>> sd = DH5('somedata.h5', mode='w', overwrite=True)