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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 remove_pos_arg_placeholders(alias_command):
 """ Remove positional argument placeholders from alias_command. Args: alias_command: The alias command to remove from. Returns: The alias command string without positional argument placeholder. """

    # Boundary index is the index at which named argument or positional argument starts
    split_command = shlex.split(alias_command)
    boundary_index = len(split_command)
    for i, subcommand in enumerate(split_command):
        if not re.match('^[a-z]', subcommand.lower()) or i > COLLISION_CHECK_LEVEL_DEPTH:
            boundary_index = i
            break

    return ' '.join(split_command[:boundary_index]).lower()