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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 decrypt_var(source, passphrase=None):
 """Attempts to decrypt a variable"""

    cmd = [gnupg_bin(), "--decrypt", gnupg_home(), gnupg_verbose(),
           passphrase_file(passphrase)]

    return stderr_with_input(flatten(cmd), source)