fix rfmult

[pep8speaks]

Hello @rdemaria! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file pysixtrack/elements.py:

Line 260:60: W291 trailing whitespace Line 269:70: E502 the backslash is redundant between brackets Line 270:17: E128 continuation line under-indented for visual indent Line 274:76: E502 the backslash is redundant between brackets Line 275:17: E128 continuation line under-indented for visual indent Line 277:37: E225 missing whitespace around operator

• In the file pysixtrack/mathlibs.py:

Line 3:1: E302 expected 2 blank lines, found 1 Line 6:1: W293 blank line contains whitespace Line 12:1: W391 blank line at end of file

• In the file pysixtrack/particles.py:

Line 394:1: W293 blank line contains whitespace Line 397:1: W293 blank line contains whitespace Line 400:43: E261 at least two spaces before inline comment

• In the file tests/test_losses.py:

Line 12:22: E225 missing whitespace around operator Line 16:51: E231 missing whitespace after ',' Line 16:53: E231 missing whitespace after ',' Line 16:55: E231 missing whitespace after ',' Line 16:57: E231 missing whitespace after ',' Line 17:55: E231 missing whitespace after ',' Line 18:1: W391 blank line at end of file