I'm working in research and trying to create a True/False factor as something like the following:

financial_health_grade = morningstar.asset_classification.financial_health_grade.latest  
    if financial_health_grade == 'D':  
        health_fail_bool = True  
    else:  
        health_fail_bool = False  

However, when executing the make_pipeline() call, I get the following error. Any idea what I am doing wrong?

AttributeErrorTraceback (most recent call last)  
<ipython-input-543-dcf250cf5490> in <module>()  
----> 1 my_pipe = make_pipeline()

<ipython-input-542-faa743d32976> in make_pipeline()  
     98           'health_fail_bool': health_fail_bool  
     99         },  
--> 100         screen=securities_to_trade  
    101     )  
    102 

/build/src/qexec_repo/zipline_repo/zipline/pipeline/pipeline.py in __init__(self, columns, screen)
     40         screen=optional(Filter),  
     41     )  
---> 42     def __init__(self, columns=None, screen=None):  
     43         if columns is None:  
     44             columns = {}

/build/src/qexec_repo/zipline_repo/zipline/pipeline/pipeline.pyc in __init__(self, columns, screen)
     46         validate_column = self.validate_column  
     47         for column_name, term in columns.items():  
---> 48             validate_column(column_name, term)  
     49             if not isinstance(term, ComputableTerm):  
     50                 raise TypeError(

/build/src/qexec_repo/zipline_repo/zipline/pipeline/pipeline.pyc in validate_column(column_name, term)
    231     @staticmethod  
    232     def validate_column(column_name, term):  
--> 233         if term.ndim == 1:  
    234             raise UnsupportedPipelineOutput(column_name=column_name, term=term)

AttributeError: 'bool' object has no attribute 'ndim'  

Edit: Figured this out right after I posted (isn't that how it always is!). For those coming up with the same problem, the solution is as follows:
health_fail_bool = financial_health_grade.element_of(['D'])