The 'check_seasons' function now raises a 'ValueError' if there is any problem with the given 'seasons' argument.

The 'check_metadata' function now raises a 'ValueError' if there is any problem with the given 'metadata' argument.

Added a function to check which of the metadata, seasons and crops arguments are needed for the given sampling method and statistics.

The 'check_data' function now raises a 'ValueError' if there is any problem with the given 'data' argument.

The 'check_statistics' function now raises a 'ValueError' if there is any problem with the given 'statistics' argument.

The 'check_sampling' function now raises a 'ValueError' if there is any problem with the given 'sampling' argument.

Added a check for the 'data_capture' argument in 'interface.py'. The check function is included in 'input_checks.py'.

Added a check for the 'crops' argument in 'interface.py'. The check function is included in 'input_checks.py'.

Made a change to directly iterate 'RSTAGS' instead of calling '.keys()' in the 'check_sampling' function in 'input_checks.py'.

Added a check for the 'seasons' argument in 'interface.py'. The check function is included in 'input_checks.py'.

Added a check for the 'metadata' argument in 'interface.py'. The check function is included in 'input_checks.py'.

Changed the argument and variable names as well as the docstring in the 'check_sampling' function in 'input_checks.py'.

Added a check for the 'data' argument in 'interface.py'. The check function is included in 'input_checks.py'.

Made some changes to the 'check_statistics' function in 'input_checks.py'. It now returns a list of functions.

Renamed 'date_times' to 'datetimes' in the argument list of 'calculate_statistics' in 'interface.py'. Also renamed local variables in the same function.

Added a check for the 'statistics' argument in 'interface.py'. The check function is included in 'input_checks.py'.

Added a check for the 'sampling' argument in 'interface.py'. The check function is included in 'input_checks.py'.

Added a class which will act as the internal data structure for this package. It is included in 'data_structure.py'.

Added a 'CHANGELOG.md' and a 'LICENSE' file. Modified the 'README.md' and added files for packaging. Created package version 0.1.0.

Made a small change to the module docstring of 'stats_utils.py'. Changed the 'CLIMATIC_ZONE' constant from an OrderedDict to a regular dict.

Redid the docstrings in 'ozone_metrics.py' and made some small code changes. Moved some functions from 'ozone_metrics.py' to 'stats_utils.py'.

Changed the argument 'df' to 'data' in the main interface of the 'toarstats' package. Made some other small adjustments to 'stats_main.py'.