fix: In the variable aggregation strategy that returns the first non-null value of each group, empty strings, empty lists, and empty objects are not treated as null values

[shaohuzhang1]

fix: In the variable aggregation strategy that returns the first non-null value of each group, empty strings, empty lists, and empty objects are not treated as null values

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[shaohuzhang1]

The provided code has a few minor issues and improvements that can be made:

1. Redundant Condition: The current condition if isinstance(v, (str,list,dict)) and len(v) == 0 is redundant because an empty string ('') or other falsy values won't evaluate to True. Therefore, you can simplify this part of the check to just v is not None.

2. Line Length: There's one line too long, which might make it harder to read. You can break the line using parentheses or a backslash.

3. Whitespace Improvements: Ensure consistent indentation to maintain readability.

Here's the improved version:

def get_first_non_null(self, variable_list):
    for variable in variable_list:
        ref_var = self.workflow_manage.get_reference_field(
            variable.get('variable')[0],
            variable.get('variable')[1:]
        )
        if ref_var is not None:
            return ref_var
    return None

Note: This assumes that ref_var returned from get_reference_field() cannot be considered "null" in the sense defined by checking its truthiness after stripping whitespace if needed (though strings are inherently non-empty in Python). If that assumption changes, additional checks should be implemented accordingly.