Python Pyx: bar graph y-axis height

I wanna make a bar graph plot in PyX (see here) using the code

 from pyx import *
 g = graph.graphxy(width=8, x=graph.axis.bar())
 g.plot(graph.data.file("minimal.dat", xname=0, y=2), [graph.style.bar()])
 g.writePDFfile("minimal")

and the data

1   0.4
2   0.5 
3   0.2
4   0.1
5   0.0

I get the plot

Question: how to force the y-axis maximum to be 1.0 instead of 0.5?

Searching pyx bar y limit in Google I found [PyX-user] How do I set ymin for a bargraph?

It suggests to create own y axis with max=

axis_y = graph.axis.linear(max=1)  # ,title="y axis")

g = graph.graphxy(width=8, x=graph.axis.bar(), y=axis_y)

and this gives me expected result.

Later I found other example which uses x_max=... directly in graphxy
so I tried y_max and it works.

g = graph.graphxy(width=8, x=graph.axis.bar(), y_max=1)

PyX — Python graphics package

Full working code used for tests.

I use io.String only to create file-like object in memory - so everyone can simply copy and test it.

from pyx import *
import io

file_obj = io.StringIO("""
1   0.4
2   0.5 
3   0.2
4   0.1
5   0.0
""")

#axis_y = graph.axis.linear(max=1, title="y axis")
#g = graph.graphxy(width=8, x=graph.axis.bar(), y=axis_y)
g = graph.graphxy(width=8, x=graph.axis.bar(), y_max=1)

# g.plot(graph.data.file("minimal.dat", xname=0, y=2), [graph.style.bar()])

g.plot(graph.data.file(file_obj, xname=0, y=2), [graph.style.bar()])

g.writePDFfile("minimal")