[BUG] Incorrect import path when using relative grafts

[amykyta3]

If grafting using a relative import path, the import path gets resolved incorrectly.
Eg:

# Assume the following module structure:
mymod.mod.mod_ral
mymod.top_ral

When grafting mod_ral onto top_ral, one would expect to provide the import path as: .mod.mod_ral

However the runtime ends up resolving this as: mymod.top_ral.mod.mod_ral

TODO

• Add unit tests to cover relative imports
• Fix the issue
• Also fix: ImportError text is missing a trailing quote for the source module name