<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_arrow(self, tipLoc, tail=None, arrow=arrow.default):
 """This method adds a straight arrow that points to @var{TIPLOC}, which is a tuple of integers. @var{TAIL} specifies the starting point of the arrow. It is either None or a string consisting of the following letters: 'l', 'c', 'r', 't', 'm,', and 'b'. Letters 'l', 'c', or 'r' means to start the arrow from the left, center, or right of the text box, respectively. Letters 't', 'm', or 'b' means to start the arrow from the top, middle or bottom of the text box. For example, when @samp{tail = 'tc'} then arrow is drawn from top-center point of the text box. ARROW specifies the style of the arrow. <<arrow>>. """

        self._arrows.append((tipLoc, tail, arrow))