Update the docs

Author: mdmintz

help_docs/useful_grep_commands.md

@@ -12,13 +12,13 @@ OR
 
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-#### Replace all occurrences of "foo_abc" with "bar_xyz" on Linux, from the current directory:
+#### Replace all occurrences of "foo_abc" with "bar_xyz" on Linux, for Python files from the current directory:
 
-``sed -i 's/foo_abc/bar_xyz/g' *``
+``sed -i 's/foo_abc/bar_xyz/g' *.py``
 
-#### Replace all occurrences of "foo_abc" with "bar_xyz" on macOS (file-backup required), from the current directory:
+#### Replace all occurrences of "foo_abc" with "bar_xyz" on macOS, for Python files from the current directory:
 
-``sed -i '.bak' 's/foo_abc/bar_xyz/g' *``
+``sed -i '' 's/foo_abc/bar_xyz/g' *.py``
 
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mkdocs_build/requirements.txt

@@ -4,7 +4,8 @@ docutils==0.18.1
 python-dateutil==2.8.2
 livereload==2.6.3;python_version>="3.6"
 joblib==1.1.0;python_version>="3.6"
-Markdown==3.3.6;python_version>="3.6"
+Markdown==3.2.2;python_version>="3.6" and python_version<"3.7"
+Markdown==3.3.6;python_version>="3.7"
 MarkupSafe==2.0.1;python_version>="3.6"
 pyparsing==3.0.7;python_version>="3.6"
 keyring==23.5.0;python_version>="3.7"