v2021.3.4

• Backwards incompatible Pymatgen root imports have been removed from
  v2021.3.4 in preparation for a change to a more modular, extensible
  architecture that will allow more developers to contribute. If your existing
  code uses from pymatgen import <something>, you will need to make
  modifications. The easiest way is to use an IDE to run a Search and Replace.
  First, replace any from pymatgen import MPRester with
  from pymatgen.ext.matproj import MPRester. Then, replace
  from pymatgen import with from pymatgen.core import. Alternative, if you
  are using a Mac command line, you can do::