conda

Version: 1.2.2

Summary of issue
Including a @dataclass decorated class breaks getsource in show_doc

Minimal example

• Clone nbdev_tutorial
• Add new cell in 00_core.ipynb

#export
from dataclasses import dataclass

@dataclass
class Foo:
    a: int
    b: str
    c: float

• Run nbdev_build_lib
• Run nbdev_build_docs

nbdev_build_docs

Is your feature request related to a problem? Please describe.
grayskull will identify licenses by fuzzy match in some cases and then suggest the best result. However, sometimes the fuzzy match scores a bit lower than average because some people modify popular licenses like BSD or MIT and add their own clauses. This kind of change will turn those into a different license altogether, which