old_contents: from coincurve.context import GLOBAL_CONTEXT, Context
  from coincurve.keys import PrivateKey, PublicKey
  from coincurve.utils import verify_signature
  
new_contents: from coincurve.context import GLOBAL_CONTEXT, Context
  from coincurve.keys import PrivateKey, PublicKey
  from coincurve.utils import verify_signature
  
  __all__ = [
      'GLOBAL_CONTEXT',
      'Context',
      'PrivateKey',
      'PublicKey',
      'verify_signature',
  ]
  
subject: Add __all__ (#113)