def unique_variable_finder(key):
    """
    Attempts to find a variable and return its handle by a key.
    Raises error if none found or multiple matches occur.

    :param key:
    :return:
    """
    variables = tf.get_collection(tf.GraphKeys.GLOBAL_VARIABLES)
    variable_names = [variable.name for variable in variables]
    found = 0
    for i, variable_name in enumerate(variable_names):
        if key in variable_name:
            found += 1
            return_me = variables[i]
    assert found > 0, 'Variable not found.'
    assert found < 2, 'Multiple matches found.'
    return return_me

def variable_finder(key):
    """
    Attempts to find variables and return their handles in a list.
    Raises error if none found.

    :param key:
    :return:
    """
    variables = tf.get_collection(tf.GraphKeys.GLOBAL_VARIABLES)
    variable_names = [variable.name for variable in variables]
    return_me = []
    found = 0
    for i, variable_name in enumerate(variable_names):
        if key in variable_name:
            found += 1
            return_me.append(variables[i])
    assert found > 0, 'Variable not found.'
    return return_me