code: def transform(self, maps):
          
          out = {}
          out["chi_p"] = conversions.chi_p(
                               maps[parameters.mass1], maps[parameters.mass2],
                               maps[parameters.spin1x], maps[parameters.spin1y],
                               maps[parameters.spin2x], maps[parameters.spin2y])
          return self.format_output(maps, out)
docs: This function transforms from component masses and caretsian spins
          to chi_p.
  
          Parameters
          ----------
          maps : a mapping object
  
          Examples
          --------
          Convert a dict of numpy.array:
  
          Returns
          -------
          out : dict
              A dict with key as parameter name and value as numpy.array or float
              of transformed values.