You can use a for loop to loop through all the nodes in a flow. For example, the following two script examples loop through all nodes and change field names in any Filter nodes to uppercase.

You can use this script in any flow that contains a Filter node, even if no fields are actually filtered. Simply add a Filter node that passes all fields in order to change field names to uppercase across the board.

# Alternative 1: using the data model nameIterator() function
stream = modeler.script.stream()
for node in stream.iterator():
    if (node.getTypeName() == "filter"):
        # nameIterator() returns the field names
        for field in node.getInputDataModel().nameIterator():
            newname = field.upper()
            node.setKeyedPropertyValue("new_name", field, newname)

# Alternative 2: using the data model iterator() function
stream = modeler.script.stream()
for node in stream.iterator():
    if (node.getTypeName() == "filter"):
        # iterator() returns the field objects so we need
        # to call getColumnName() to get the name
        for field in node.getInputDataModel().iterator():
            newname = field.getColumnName().upper()
            node.setKeyedPropertyValue("new_name", field.getColumnName(), newname)

The script loops through all nodes in the current flow, and checks whether each node is a Filter. If so, the script loops through each field in the node and uses either the field.upper() or field.getColumnName().upper() function to change the name to uppercase.