whole_func_string: function discoverFromHeaders (webId) {
    return fetch(webId, { method: 'OPTIONS' })
      .then(response => {
        if (response.ok) {
          return parseProviderLink(response.headers)
        }
  
        return null
      })
  }
func_code_string: function discoverFromHeaders (webId) {
    return fetch(webId, { method: 'OPTIONS' })
      .then(response => {
        if (response.ok) {
          return parseProviderLink(response.headers)
        }
  
        return null
      })
  }
func_documentation_string: @param webId {string}
  
  @returns {Promise<string|null>}