prefer 'key in dict' instead of 'dict.has_key()'
prefer 'key in dict' instead of 'dict.has_key()'

modern python prefers `if key in dictionary` instead of
`if dictionary.has_key(key)`.

ipfs/py-ipfs-api,alexander255/py-ipfs-api,ipfs/python-ipfs-api,moreati/python-ipfs-api,alexander255/py-ipfs-api,ipfs/py-ipfs-api