<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_mapping(parser, mapped):
 """Gets the original file name for a module that was mapped when the module name does not coincide with the file name that the module was defined in."""

    if mapped in parser.mappings:
        return parser.mappings[mapped]
    else:
        return mapped + ".f90"