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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def build_flex_args_keys(components):
 """ Helper function to build a list of options. Some tools require require variations of the same options (e.g., cflags for debug vs release builds), but manually creating those options is cumbersome and error-prone. This function handles that work by combining all possible comintations of the values in components. Arguments components -- A list of lists that should be combined to form options. """


    def _prepend_first(components, sub_components):
        ret = []
        for first in components[0]:
            for sub_component in sub_components:
                ret.append("{}.{}".format(first, sub_component))
        return ret

    if len(components) > 1:
        sub_components = build_flex_args_keys(components[1:])
        return _prepend_first(components, sub_components)
    if len(components) == 1:
        return components[0]
    return []