Returns the name of the caller's module as a string.

    >>> get_caller_module()
    '__main__'

def get_caller_module():
    """
    Returns the name of the caller's module as a string.

    >>> get_caller_module()
    '__main__'
    """
    stack = inspect.stack()
    assert len(stack) > 1
    caller = stack[2][0]
    return caller.f_globals['__name__']