Update docs/Users_Guide/data_io.rst

Co-authored-by: Dan Adriaansen <[email protected]>

docs/Users_Guide/data_io.rst

@@ -33,7 +33,7 @@ ASCII file lists consist of a white-space separated list of paths to the input f
 
 The file list elements can be separated by spaces, tabs, or newlines, but not commas. Users are encouraged to add the optional **file_list** keyword as the first element of each list to clearly identify it as such. When **file_list** is the first item, no validation of the file existence is performed. When **file_list** is not present, MET checks whether each input file actually exists on the file system and errors out if it encounters too many missing input files.
 
-While this validation logic is useful for standard input file formats, it can cause problems when providing a list of arguments for a Python embedding script since those arguments may not actually be the names of files on the file system. Please see the description of :ref:`MET_PYTHON_INPUT_ARG <met-python-input-arg>` for additional details.
+While validating file existence is useful for standard input file formats, it can cause problems when providing a list of arguments for a Python embedding script since a **file_list** used for Python embedding can contain optional command line arguments in addition to file names on each line. Please see the description of :ref:`MET_PYTHON_INPUT_ARG <met-python-input-arg>` for additional details.
 
 Here is an example ASCII file list for three input files, each listed on a separate line: