code: def test_element_line_dashed_capstyle():
      p = ggplot(mtcars, aes(x="wt", y="mpg")) + theme(
          panel_grid=element_line(
              linetype="dashed",
              lineend="butt",
              size=1.0,
          )
      )
      # no exception
      p._build()
  
imports: import os
  import pytest
  from plotnine import aes, element_blank, element_line, element_text, facet_grid, facet_wrap, geom_blank, geom_point, ggplot, labs, theme, theme_538, theme_bw, theme_classic, theme_dark, theme_gray, theme_light, theme_linedraw, theme_matplotlib, theme_minimal, theme_seaborn, theme_tufte, theme_void, theme_xkcd
  from plotnine.data import mtcars
label_desc: Use image node_id 7 for calling a global function with example usage: test_element_line_dashed_capstyle() without return types