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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 is_valid_release_version(version):
    '''Checks that the given version code is valid.'''
    return version is not None and len(version) == 6 and version[0] == 'R' \
            and int(version[1:5]) in range(1990, 2050) \
            and version[5] in ('h', 'g', 'f', 'e', 'd', 'c', 'b', 'a')