docs: def copy(self, only=None):
          '''
          Returns a deep copy with all of the numpy arrays copied
          If only is a list of strings, i.e. ['f', 'v'], then only those properties will be copied
          '''
          if only is None:
              return Mesh(self)
          else:
              import copy
              m = Mesh()
              for a in only:
                  setattr(m, a, copy.deepcopy(getattr(self, a)))
              return m