def getTreeString(x, y, z, numLogs):
    """ Returns a Malmo string to use in the mission XML to create a tree. """
    leavesHeight = y + 4
    treeHeight = y + numLogs
    return """
		<DrawingDecorator>
			<DrawSphere x="{x}" y="{yLeaves}" z="{z}" radius="3" type="leaves" />
			<DrawLine x1="{x}" y1="{y}" z1="{z}" x2="{x}" y2="{yTreeHeight}" z2="{z}" type="log" />
		</DrawingDecorator>""".format(x=x, y=y, z=z, yLeaves=leavesHeight, yTreeHeight=treeHeight)