span>

<span class='kw'>def</span> <span class='id identifier rubyid_add'>add</span><span class='lparen'>(</span><span class='id identifier rubyid_balance'>balance</span><span class='rparen'>)</span>
  <span class='id identifier rubyid_raise'>raise</span> <span class='const'>ArgumentError</span><span class='comma'>,</span> <span class='tstring'><span class='tstring_beg'>&#39;</span><span class='tstring_content'>balance must be a Coinbase::Balance</span><span class='tstring_end'>&#39;</span></span> <span cla