<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def describe_file_set(modules):
 """Build a file set from a specified Python modules. Args: modules: Iterable of Python module to describe. Returns: Initialized FileSet instance describing the modules. """

    descriptor = FileSet()
    file_descriptors = []
    for module in modules:
        file_descriptors.append(describe_file(module))

    if file_descriptors:
        descriptor.files = file_descriptors

    return descriptor