The dmi_is_open function tells whether a context holds SMBIOS
data: a structure table and the registry of its structures, which
dmi_open and dmi_load fill the context with, and dmi_close
frees.
The function is defined inline in the header, and reads the state of the
context only.
Parameters
context
Context in question, which must not be nullptr.
Return value
Returns true if the context is open, and false otherwise.