Create a Python function to filter a dictionary that contains strings only.
{'name': 'John', 'age': 20, 'likes': ['apple', 'banana']}
def filterStringDict(input):
    result = {}
    for key, value in input.items():
        # Check if value is a string
        if isinstance(value, str):
            # Add to result
            result[key] = value
    return result