Retrieves the character vector of custom columns for a given method.
These are method-specific columns beyond the standard columns
(method, estimate, standard_error, ci_lower, ci_upper, p_value, BF,
convergence, note) that each method returns.
When implementing new methods, consider using standardized column names
for consistency:
- Heterogeneity
tau_estimate, tau_ci_lower, tau_ci_upper,
tau_p_value, tau_BF
- Publication Bias
bias_coefficient, bias_coefficient_se,
bias_p_value, bias_BF