code: def symmetry(self, input_entity, coefficients, duplicate=True):
          
          d = {1: "Line", 2: "Surface", 3: "Volume"}
          entity = "{}{{{}}};".format(d[input_entity.dimension], input_entity.id)
  
          if duplicate:
              entity = "Duplicata{{{}}}".format(entity)
  
          self._GMSH_CODE.append(
              "Symmetry {{{}}} {{{}}}".format(
                  ", ".join([str(co) for co in coefficients]), entity
              )
          )
          return
docs: Transforms all elementary entities symmetrically to a plane. The vector
          should contain four expressions giving the coefficients of the plane's equation.