This error is usually caused by using a Var, unit, or mutable Param in a Boolean context such as an "if" statement, or when checking container membership or equality. For example, >>> m.x = Var() >>> if m.x >= 1: ... pass and >>> m.y = Var() >>> if m.y in [m.x, m.y]: ... pass would both cause this exception.

The error message you mentioned usually occurs when you use a variable, unit, or mutable parameter in a Boolean context, such as an "if" statement or when checking container membership or equality.

To resolve this issue, you can modify your code accordingly. Here are a few examples of how to fix this error:

1. If you want to check the value of a variable in an "if" statement, you should compare its value using the `value()` function:

if value(m.x) >= 1:
    pass

2. If you want to check if a variable is in a list, you can compare the variable itself rather than the variable object:

if m.y in [m.x, m.y]:
    pass

3. If you want to check if a parameter is in a set or list, you can also compare the parameter value instead of the parameter object:

if m.param_value in [1, 2, 3]:
    pass

By following these suggestions, you should be able to resolve the error caused by using a variable, unit, or mutable parameter in a Boolean context.

Please let me know if you have any further questions!