def METHOD_NAME(self, fld_name, bit_width, access_type, reset_val = 0):
    new_fld = riscv_reg_field()
    new_fld.bit_width = bit_width
    new_fld.access_type = access_type
    new_fld.reset_val = reset_val
    new_fld.name = fld_name
    self.fld.append(new_fld)  # insert(index, value) is not supported in PyVSC