Solve the programming task below in a Python markdown code block.
### Background

We **all** know about "balancing parentheses" (plus brackets, braces and chevrons) and even balancing characters that are identical.  

Read that last sentence again, I balanced different characters and identical characters twice and you didn't even notice... :)

### Kata
Your challenge in this kata is to write a piece of code to validate that a supplied string is balanced.

You must determine if all that is open is then closed, and nothing is closed which is not already open!

You will be given a string to validate, and a second string, where each pair of characters defines an opening and closing sequence that needs balancing.

You may assume that the second string always has an even number of characters.

### Example
```python
# In this case '(' opens a section, and ')' closes a section
is_balanced("(Sensei says yes!)", "()")       # => True
is_balanced("(Sensei says no!", "()")         # => False

# In this case '(' and '[' open a section, while ')' and ']' close a section
is_balanced("(Sensei [says] yes!)", "()[]")   # => True
is_balanced("(Sensei [says) no!]", "()[]")    # => False

# In this case a single quote (') both opens and closes a section
is_balanced("Sensei says 'yes'!", "''")       # => True
is_balanced("Sensei say's no!", "''")         # => False
```
Also feel free to reuse/extend the following starter code:
```python
def is_balanced(source, caps):
```