Fix syntax warnings

[tueda]

With Python 3.12 (w/o .pyc cache files in __pycache__), by importing madminer,

import madminer

I got the following warnings:

/home/tueda/work/madminer/madminer/utils/interfaces/mg.py:268: SyntaxWarning: invalid escape sequence '\$'
  replacement_command = """sed -e 's@\$mgprocdir@'"$mgprocdir"'@' {}/{} > {}/{}""".format(
/home/tueda/work/madminer/madminer/fisherinformation/geometry.py:164: SyntaxWarning: invalid escape sequence '\p'
  """
/home/tueda/work/madminer/madminer/fisherinformation/geometry.py:187: SyntaxWarning: invalid escape sequence '\p'
  """
/home/tueda/work/madminer/madminer/fisherinformation/geometry.py:349: SyntaxWarning: "is not" with 'int' literal. Did you mean "!="?
  if self.dimension is not 2:

This patch resolves these warnings.

The last warning SyntaxWarning: "is not" with 'int' literal may need some explanation: indeed, I expect the current code to work correctly due to CPython's optimization of small integers (from -5 to 256),

x = 2
print(x is 2)  # prints True

but using is for integer comparison in general can lead to incorrect results. For example, the following code gives a counterintuitive result:

x = 257
print(x is 257)  # prints False

[matthewfeickert]

Thanks for the PR @tueda! I'm traveling at the moment and so just seeing this, but I can review it tomorrow.

[Merosmsm]

[Merosmsm]

[Merosmsm]

Hola

[Merosmsm]

Hola
/home/tueda/work/madminer/madminer/utils/interfaces/mg.py:268: SyntaxWarning: invalid escape sequence '$'
replacement_command = """sed -e 's@$mgprocdir@'"$mgprocdir"'@' {}/{} > {}/{}""".format(
/home/tueda/work/madminer/madminer/fisherinformation/geometry.py:164: SyntaxWarning: invalid escape sequence '\p'
"""
/home/tueda/work/madminer/madminer/fisherinformation/geometry.py:187: SyntaxWarning: invalid escape sequence '\p'
"""
/home/tueda/work/madminer/madminer/fisherinformation/geometry.py:349: SyntaxWarning: "is not" with 'int' literal. Did you mean "!="?
if self.dimension is not 2: