Returns the values associated with key under group_name as
doubles.
If key cannot be found then NULL is returned and error is set to
G_KEY_FILE_ERROR_KEY_NOT_FOUND Likewise, if the values associated
with key cannot be interpreted as doubles then NULL is returned
and error is set to G_KEY_FILE_ERROR_INVALID_VALUE
the values associated with the key as a list of doubles, or NULL if the
key was not found or could not be parsed. The returned list of doubles
should be freed with g_free() when no longer needed.
Returns the values associated with key under group_name as doubles.
If key cannot be found then NULL is returned and error is set to G_KEY_FILE_ERROR_KEY_NOT_FOUND Likewise, if the values associated with key cannot be interpreted as doubles then NULL is returned and error is set to G_KEY_FILE_ERROR_INVALID_VALUE