combine_weights.py

def combine_weights(in_list):
    """
    Returns a 1D tensor of the input list of (nested lists of) tensors, useful
    for doing things like comparing current weights with old weights for EWC.
    
    1.) For all elements in input list, (ln 3)
          if a list combine it recursively 
          else leave it alone
    2.) From resulting list, get all non-none elements and flatten them (ln 2)
    3.) If resulting list is empty return None (ln 1)
          else return concatenation of list
    ( All on one line :) )
    """
    
    return (lambda x: None if not x else tf.concat(x, axis=0)) (
        [ tf.reshape(x, [-1]) for x in
        [ combine_weights(x) if isinstance(x, list) else x for x in in_list ]
        if x is not None])